MacでFiddlerが起動しない場合の解消方法

# 発生事象
Fiddlerを起動しようとすると下記エラーが発生し、起動できなかった。

```
$ mono Fiddler.exe
WARNING: The Carbon driver has not been ported to 64bits, and very few parts of Windows.Forms will work properly, or at all
Stacktrace:

  at <unknown> <0xffffffff>
  at (wrapper managed-to-native) System.Windows.Forms.XplatUICarbon.CGDisplayBounds (intptr) [0x00002] in <94e9aaa501e644b0901ffbcf255e8722>:0
  at System.Windows.Forms.XplatUICarbon.get_WorkingArea () [0x00005] in <94e9aaa501e644b0901ffbcf255e8722>:0
  at System.Windows.Forms.XplatUICarbon.get_VirtualScreen () [0x00000] in <94e9aaa501e644b0901ffbcf255e8722>:0
  at System.Windows.Forms.XplatUI.get_VirtualScreen () [0x00000] in <94e9aaa501e644b0901ffbcf255e8722>:0
  at System.Windows.Forms.Screen..cctor () [0x00034] in <94e9aaa501e644b0901ffbcf255e8722>:0
  at (wrapper runtime-invoke) object.runtime_invoke_void (object,intptr,intptr,intptr) [0x0001e] in <ab7d7c14aa7a405ca7d85082a965a195>:0
  at <unknown> <0xffffffff>
  at System.Windows.Forms.Form.get_CreateParams () [0x00157] in <94e9aaa501e644b0901ffbcf255e8722>:0
  at System.Windows.Forms.Control.CreateHandle () [0x0002a] in <94e9aaa501e644b0901ffbcf255e8722>:0
  at System.Windows.Forms.Form.CreateHandle () [0x00000] in <94e9aaa501e644b0901ffbcf255e8722>:0
  at System.Windows.Forms.Control.CreateControl () [0x00039] in <94e9aaa501e644b0901ffbcf255e8722>:0
  at System.Windows.Forms.Control.SetVisibleCore (bool) [0x00057] in <94e9aaa501e644b0901ffbcf255e8722>:0
  at System.Windows.Forms.Form.SetVisibleCore (bool) [0x00065] in <94e9aaa501e644b0901ffbcf255e8722>:0
  at System.Windows.Forms.Control.set_Visible (bool) [0x00009] in <94e9aaa501e644b0901ffbcf255e8722>:0
  at System.Windows.Forms.Control.Show () [0x00000] in <94e9aaa501e644b0901ffbcf255e8722>:0
  at (wrapper remoting-invoke-with-check) System.Windows.Forms.Control.Show () [0x00031] in <94e9aaa501e644b0901ffbcf255e8722>:0
  at Fiddler.frmViewer. (string[]) [0x00081] in <09623c708fdb40a483cea147bbea7a7f>:0
  at Fiddler.frmViewer. (string[]) [0x00016] in <09623c708fdb40a483cea147bbea7a7f>:0
  at (wrapper runtime-invoke) <Module>.runtime_invoke_void_object (object,intptr,intptr,intptr) [0x0004e] in <09623c708fdb40a483cea147bbea7a7f>:0
Memory around native instruction pointer (0x7fff68b41c9b):
0x7fff68b41c8b  53 50 48 89 fb 48 8b 05 a1 53 82 38 48 8b 48 18  SPH..H...S.8H.H.
0x7fff68b41c9b  48 89 4b 18 48 8b 48 10 48 89 4b 10 48 8b 08 48  H.K.H.H.H.K.H..H
0x7fff68b41cab  8b 40 08 48 89 43 08 48 89 0b 89 f7 48 89 de e8  .@.H.C.H....H...
0x7fff68b41cbb  68 80 fc ff 48 89 d8 48 83 c4 08 5b 5d c3 55 48  h...H..H...[].UH

Native stacktrace:

Pkilling 0x70000ed51000 from 0x103c335c0
Pkilling 0x70000ea48000 from 0x103c335c0
Entering thread summarizer pause from 0x103c335c0
Finished thread summarizer pause from 0x103c335c0.

Waiting for dumping threads to resume


Debug info from gdb:

(lldb) command source -s 0 '/tmp/mono-gdb-commands.nTVz7X'
Executing commands in '/tmp/mono-gdb-commands.nTVz7X'.
(lldb) process attach --pid 20055
warning: (x86_64) /Library/Frameworks/Mono.framework/Versions/5.18.0/lib/mono/4.5/mscorlib.dll.dylib empty dSYM file detected, dSYM was created with an executable with no debug info.
warning: (x86_64) /Library/Frameworks/Mono.framework/Versions/5.18.0/lib/libglib-2.0.0.dylib empty dSYM file detected, dSYM was created with an executable with no debug info.
Process 20055 stopped
* thread #1, name = 'tid_307', queue = 'com.apple.main-thread', stop reason = signal SIGSTOP
    frame #0: 0x00007fff6fbbd2d2 libsystem_kernel.dylib`__wait4 + 10
libsystem_kernel.dylib`__wait4:
->  0x7fff6fbbd2d2 <+10>: jae    0x7fff6fbbd2dc            ; <+20>
    0x7fff6fbbd2d4 <+12>: movq   %rax, %rdi
    0x7fff6fbbd2d7 <+15>: jmp    0x7fff6fbb8381            ; cerror
    0x7fff6fbbd2dc <+20>: retq   
Target 0: (mono) stopped.

Executable module set to "/Library/Frameworks/Mono.framework/Versions/Current/Commands/mono".
Architecture set to: x86_64h-apple-macosx.
(lldb) thread list
Process 20055 stopped
* thread #1: tid = 0x12ea25, 0x00007fff6fbbd2d2 libsystem_kernel.dylib`__wait4 + 10, name = 'tid_307', queue = 'com.apple.main-thread', stop reason = signal SIGSTOP
  thread #2: tid = 0x12ea26, 0x00007fff6fbbb7de libsystem_kernel.dylib`__psynch_cvwait + 10, name = 'SGen worker'
  thread #3: tid = 0x12ea27, 0x00007fff6fbb81b6 libsystem_kernel.dylib`semaphore_wait_trap + 10, name = 'Finalizer'
  thread #4: tid = 0x12ea28, 0x00007fff6fbb9b6a libsystem_kernel.dylib`__workq_kernreturn + 10
  thread #5: tid = 0x12ea29, 0x00007fff6fbb9b6a libsystem_kernel.dylib`__workq_kernreturn + 10
  thread #6: tid = 0x12ea3e, 0x00007fff6fbbb7de libsystem_kernel.dylib`__psynch_cvwait + 10, name = 'Timer-Scheduler'
  thread #7: tid = 0x12ea43, 0x00007fff6fbbb7de libsystem_kernel.dylib`__psynch_cvwait + 10, name = 'tid_a803'
  thread #8: tid = 0x12ea44, 0x00007fff6fbb81ce libsystem_kernel.dylib`semaphore_timedwait_trap + 10, name = 'Thread Pool Worker'
  thread #9: tid = 0x12ea45, 0x00007fff6fbb81ce libsystem_kernel.dylib`semaphore_timedwait_trap + 10, name = 'Thread Pool Worker'
(lldb) thread backtrace all
* thread #1, name = 'tid_307', queue = 'com.apple.main-thread', stop reason = signal SIGSTOP
  * frame #0: 0x00007fff6fbbd2d2 libsystem_kernel.dylib`__wait4 + 10
    frame #1: 0x0000000100973813 mono`mono_dump_native_crash_info at mini-posix.c:1041 [opt]
    frame #2: 0x00000001009736c1 mono`mono_dump_native_crash_info(signal="SIGSEGV", ctx=<unavailable>, info=<unavailable>) at mini-posix.c:1064 [opt]
    frame #3: 0x0000000100917383 mono`mono_handle_native_crash(signal="SIGSEGV", ctx=0x0000000100f92f48, info=0x0000000100f92ee0) at mini-exceptions.c:3197 [opt]
    frame #4: 0x000000010086ce26 mono`mono_sigsegv_signal_handler(_dummy=<unavailable>, _info=0x0000000100f92ee0, context=0x0000000100f92f48) at mini-runtime.c:3486 [opt]
    frame #5: 0x00007fff6fc69b3d libsystem_platform.dylib`_sigtramp + 29
    frame #6: 0x00007fff68b41c9c SkyLight`SLDisplayBounds + 21
    frame #7: 0x0000000107790fbe
    frame #8: 0x0000000100f7b526
    frame #9: 0x0000000100870253 mono`mono_jit_runtime_invoke(method=<unavailable>, obj=<unavailable>, params=0x0000000000000000, exc=0x00000001077909f0, error=<unavailable>) at mini-runtime.c:3148 [opt]
    frame #10: 0x0000000100a6e034 mono`do_runtime_invoke(method=0x00007fc99d8575d0, obj=0x0000000000000000, params=0x0000000000000000, exc=0x00007ffeef3a19b8, error=0x00007ffeef3a1b98) at object.c:2960 [opt]
    frame #11: 0x0000000100a6a008 mono`mono_runtime_class_init_full [inlined] mono_runtime_try_invoke(method=<unavailable>, obj=<unavailable>, params=<unavailable>, error=0x00007ffeef3a1b98) at object.c:3069 [opt]
    frame #12: 0x0000000100a69fc7 mono`mono_runtime_class_init_full(vtable=0x00007fc99d039400, error=0x00007ffeef3a1b98) at object.c:526 [opt]
    frame #13: 0x0000000100868805 mono`mono_jit_compile_method_inner(method=0x00007fc99d857458, target_domain=0x00007fc99c60b1b0, opt=<unavailable>, error=0x00007ffeef3a1b98) at mini.c:4184 [opt]
    frame #14: 0x000000010086bd49 mono`mono_jit_compile_method_with_opt(method=0x00007fc99d857458, opt=<unavailable>, jit_only=0, error=0x00007ffeef3a1b98) at mini-runtime.c:2411 [opt]
    frame #15: 0x000000010091a244 mono`common_call_trampoline(regs=0x00007ffeef3a1c68, code=<unavailable>, m=0x00007fc99d857458, vt=0x0000000000000000, vtable_slot=<unavailable>, error=0x00007ffeef3a1b98) at mini-trampolines.c:755 [opt]
    frame #16: 0x0000000100919c89 mono`mono_magic_trampoline(regs=0x00007ffeef3a1c68, code="H\x8b?H??\xa8H\x8b??8, arg=0x00007fc99d857458, tramp=<unavailable>) at mini-trampolines.c:895 [opt]
    frame #17: 0x0000000100d81393
    frame #18: 0x00000001074685fb
    frame #19: 0x0000000103d7f16f
    frame #20: 0x0000000103d7ee47
    frame #21: 0x0000000100f7b053
    frame #22: 0x0000000100870253 mono`mono_jit_runtime_invoke(method=<unavailable>, obj=<unavailable>, params=0x00007ffeef3a24f8, exc=0x00000001010577d8, error=<unavailable>) at mini-runtime.c:3148 [opt]
    frame #23: 0x0000000100a6e034 mono`do_runtime_invoke(method=0x00007fc99c60c948, obj=0x0000000000000000, params=0x00007ffeef3a24f8, exc=0x0000000000000000, error=0x00007ffeef3a2530) at object.c:2960 [opt]
    frame #24: 0x0000000100a71b0c mono`do_exec_main_checked [inlined] mono_runtime_invoke_checked(method=<unavailable>, obj=<unavailable>, params=<unavailable>, error=0x00007ffeef3a2530) at object.c:3128 [opt]
    frame #25: 0x0000000100a71afd mono`do_exec_main_checked(method=0x00007fc99c60c948, args=<unavailable>, error=0x00007ffeef3a2530) at object.c:4949 [opt]
    frame #26: 0x00000001008d721d mono`mono_jit_exec at driver.g.c:1236 [opt]
    frame #27: 0x00000001008d720f mono`mono_jit_exec(domain=<unavailable>, assembly=<unavailable>, argc=1, argv=0x00007ffeef3a28e8) at driver.g.c:1195 [opt]
    frame #28: 0x00000001008da3ff mono`mono_main [inlined] main_thread_handler at driver.g.c:1313 [opt]
    frame #29: 0x00000001008da3c8 mono`mono_main(argc=2, argv=<unavailable>) at driver.g.c:2483 [opt]
    frame #30: 0x000000010085f0e8 mono`main [inlined] mono_main_with_options(argc=<unavailable>, argv=<unavailable>) at main.c:50 [opt]
    frame #31: 0x000000010085f0d4 mono`main(argc=2, argv=<unavailable>) at main.c:405 [opt]
    frame #32: 0x00007fff6fa7eed9 libdyld.dylib`start + 1
  thread #2, name = 'SGen worker'
    frame #0: 0x00007fff6fbbb7de libsystem_kernel.dylib`__psynch_cvwait + 10
    frame #1: 0x00007fff6fc75593 libsystem_pthread.dylib`_pthread_cond_wait + 724
    frame #2: 0x0000000100b3af4e mono`thread_func [inlined] mono_os_cond_wait(mutex=<unavailable>) at mono-os-mutex.h:173 [opt]
    frame #3: 0x0000000100b3af3b mono`thread_func at sgen-thread-pool.c:165 [opt]
    frame #4: 0x0000000100b3af2d mono`thread_func(data=0x0000000000000000) at sgen-thread-pool.c:196 [opt]
    frame #5: 0x00007fff6fc72305 libsystem_pthread.dylib`_pthread_body + 126
    frame #6: 0x00007fff6fc7526f libsystem_pthread.dylib`_pthread_start + 70
    frame #7: 0x00007fff6fc71415 libsystem_pthread.dylib`thread_start + 13
  thread #3, name = 'Finalizer'
    frame #0: 0x00007fff6fbb81b6 libsystem_kernel.dylib`semaphore_wait_trap + 10
    frame #1: 0x0000000100ae880a mono`finalizer_thread [inlined] mono_os_sem_wait(flags=MONO_SEM_FLAGS_ALERTABLE) at mono-os-semaphore.h:90 [opt]
    frame #2: 0x0000000100ae87ff mono`finalizer_thread at mono-coop-semaphore.h:43 [opt]
    frame #3: 0x0000000100ae87e5 mono`finalizer_thread(unused=<unavailable>) at gc.c:918 [opt]
    frame #4: 0x0000000100a93c73 mono`start_wrapper [inlined] start_wrapper_internal at threads.c:1151 [opt]
    frame #5: 0x0000000100a93be3 mono`start_wrapper(data=0x00007fc99c40e790) at threads.c:1211 [opt]
    frame #6: 0x00007fff6fc72305 libsystem_pthread.dylib`_pthread_body + 126
    frame #7: 0x00007fff6fc7526f libsystem_pthread.dylib`_pthread_start + 70
    frame #8: 0x00007fff6fc71415 libsystem_pthread.dylib`thread_start + 13
  thread #4
    frame #0: 0x00007fff6fbb9b6a libsystem_kernel.dylib`__workq_kernreturn + 10
    frame #1: 0x00007fff6fc71710 libsystem_pthread.dylib`_pthread_wqthread + 670
    frame #2: 0x00007fff6fc71405 libsystem_pthread.dylib`start_wqthread + 13
  thread #5
    frame #0: 0x00007fff6fbb9b6a libsystem_kernel.dylib`__workq_kernreturn + 10
    frame #1: 0x00007fff6fc71630 libsystem_pthread.dylib`_pthread_wqthread + 446
    frame #2: 0x00007fff6fc71405 libsystem_pthread.dylib`start_wqthread + 13
  thread #6, name = 'Timer-Scheduler'
    frame #0: 0x00007fff6fbbb7de libsystem_kernel.dylib`__psynch_cvwait + 10
    frame #1: 0x00007fff6fc755c6 libsystem_pthread.dylib`_pthread_cond_wait + 775
    frame #2: 0x0000000100b49a44 mono`mono_os_cond_timedwait(cond=0x00007fc99d81e6e0, mutex=0x00007fc99d81e6a0, timeout_ms=499) at mono-os-mutex.c:44 [opt]
    frame #3: 0x0000000100ab2279 mono`mono_w32handle_timedwait_signal_handle at mono-coop-mutex.h:102 [opt]
    frame #4: 0x0000000100ab224c mono`mono_w32handle_timedwait_signal_handle [inlined] mono_w32handle_timedwait_signal_naked(poll=0, alerted=<unavailable>) at w32handle.c:643 [opt]
    frame #5: 0x0000000100ab224c mono`mono_w32handle_timedwait_signal_handle(handle_data=<unavailable>, timeout=<unavailable>, poll=0, alerted=<unavailable>) at w32handle.c:758 [opt]
    frame #6: 0x0000000100ab2141 mono`mono_w32handle_wait_one(handle=<unavailable>, timeout=<unavailable>, alertable=<unavailable>) at w32handle.c:876 [opt]
    frame #7: 0x0000000100ab23c2 mono`mono_w32handle_wait_multiple(handles=0x000070000ed50920, nhandles=1, waitall=0, timeout=<unavailable>, alertable=1) at w32handle.c:914 [opt]
    frame #8: 0x0000000100a8e1b7 mono`ves_icall_System_Threading_WaitHandle_Wait_internal(handles=<unavailable>, numhandles=<unavailable>, waitall=<unavailable>, timeout=-1, error=0x000070000ed50840) at threads.c:2122 [opt]
    frame #9: 0x0000000107782c4d
    frame #10: 0x0000000102abd3b0 mscorlib.dll.dylib`System_Threading_WaitHandle_InternalWaitOne_System_Runtime_InteropServices_SafeHandle_long_bool_bool + 64
    frame #11: 0x0000000102abd35c mscorlib.dll.dylib`System_Threading_WaitHandle_WaitOne_long_bool + 44
    frame #12: 0x0000000102abd1c3 mscorlib.dll.dylib`System_Threading_WaitHandle_WaitOne_int_bool + 51
    frame #13: 0x0000000102abd2ec mscorlib.dll.dylib`System_Threading_WaitHandle_WaitOne_int + 28
    frame #14: 0x0000000102ac282a mscorlib.dll.dylib`System_Threading_Timer_Scheduler_SchedulerThread + 266
    frame #15: 0x0000000102ab6017 mscorlib.dll.dylib`System_Threading_ThreadHelper_ThreadStart_Context_object + 151
    frame #16: 0x0000000102ab3b81 mscorlib.dll.dylib`System_Threading_ExecutionContext_Run_System_Threading_ExecutionContext_System_Threading_ContextCallback_object_bool + 33
    frame #17: 0x0000000102ab3b14 mscorlib.dll.dylib`System_Threading_ExecutionContext_Run_System_Threading_ExecutionContext_System_Threading_ContextCallback_object + 84
    frame #18: 0x0000000102ab615f mscorlib.dll.dylib`System_Threading_ThreadHelper_ThreadStart + 47
    frame #19: 0x0000000100f87249
    frame #20: 0x0000000100870253 mono`mono_jit_runtime_invoke(method=<unavailable>, obj=<unavailable>, params=0x000070000ed50ec8, exc=0x00000001010548e8, error=<unavailable>) at mini-runtime.c:3148 [opt]
    frame #21: 0x0000000100a6e034 mono`do_runtime_invoke(method=0x00007fc99d8bf730, obj=0x0000000101054a60, params=0x000070000ed50ec8, exc=0x0000000000000000, error=0x000070000ed50e60) at object.c:2960 [opt]
    frame #22: 0x0000000100a6fdfb mono`mono_runtime_delegate_try_invoke [inlined] mono_runtime_invoke_checked(params=<unavailable>, error=<unavailable>) at object.c:3128 [opt]
    frame #23: 0x0000000100a6fdf3 mono`mono_runtime_delegate_try_invoke(delegate=0x0000000101054a60, params=0x000070000ed50ec8, exc=0x0000000000000000, error=0x000070000ed50e60) at object.c:4230 [opt]
    frame #24: 0x0000000100a93c9e mono`start_wrapper at threads.c:1159 [opt]
    frame #25: 0x0000000100a93be3 mono`start_wrapper(data=0x00007fc99c67b3e0) at threads.c:1211 [opt]
    frame #26: 0x00007fff6fc72305 libsystem_pthread.dylib`_pthread_body + 126
    frame #27: 0x00007fff6fc7526f libsystem_pthread.dylib`_pthread_start + 70
    frame #28: 0x00007fff6fc71415 libsystem_pthread.dylib`thread_start + 13
  thread #7, name = 'tid_a803'
    frame #0: 0x00007fff6fbbb7de libsystem_kernel.dylib`__psynch_cvwait + 10
    frame #1: 0x00007fff6fc755c6 libsystem_pthread.dylib`_pthread_cond_wait + 775
    frame #2: 0x0000000100b49a44 mono`mono_os_cond_timedwait(cond=0x0000000100cc36f0, mutex=0x0000000100cc36b0, timeout_ms=500) at mono-os-mutex.c:44 [opt]
    frame #3: 0x0000000100b54b37 mono`mono_thread_info_sleep at mono-coop-mutex.h:102 [opt]
    frame #4: 0x0000000100b54b0b mono`mono_thread_info_sleep [inlined] sleep_interruptable(ms=<unavailable>, alerted=<unavailable>) at mono-threads.c:1560 [opt]
    frame #5: 0x0000000100b54abd mono`mono_thread_info_sleep(ms=500, alerted=<unavailable>) at mono-threads.c:1592 [opt]
    frame #6: 0x00000001009e0c63 mono`monitor_thread(unused=<unavailable>) at threadpool-worker-default.c:708 [opt]
    frame #7: 0x0000000100a93c73 mono`start_wrapper [inlined] start_wrapper_internal at threads.c:1151 [opt]
    frame #8: 0x0000000100a93be3 mono`start_wrapper(data=0x00007fc99c412c80) at threads.c:1211 [opt]
    frame #9: 0x00007fff6fc72305 libsystem_pthread.dylib`_pthread_body + 126
    frame #10: 0x00007fff6fc7526f libsystem_pthread.dylib`_pthread_start + 70
    frame #11: 0x00007fff6fc71415 libsystem_pthread.dylib`thread_start + 13
  thread #8, name = 'Thread Pool Worker'
    frame #0: 0x00007fff6fbb81ce libsystem_kernel.dylib`semaphore_timedwait_trap + 10
    frame #1: 0x00000001009e123d mono`worker_thread [inlined] mono_os_sem_timedwait(flags=MONO_SEM_FLAGS_ALERTABLE) at mono-os-semaphore.h:124 [opt]
    frame #2: 0x00000001009e11bf mono`worker_thread at mono-coop-semaphore.h:57 [opt]
    frame #3: 0x00000001009e11a5 mono`worker_thread at threadpool-worker-default.c:391 [opt]
    frame #4: 0x00000001009e10b1 mono`worker_thread(unused=<unavailable>) at threadpool-worker-default.c:490 [opt]
    frame #5: 0x0000000100a93c73 mono`start_wrapper [inlined] start_wrapper_internal at threads.c:1151 [opt]
    frame #6: 0x0000000100a93be3 mono`start_wrapper(data=0x00007fc99c746870) at threads.c:1211 [opt]
    frame #7: 0x00007fff6fc72305 libsystem_pthread.dylib`_pthread_body + 126
    frame #8: 0x00007fff6fc7526f libsystem_pthread.dylib`_pthread_start + 70
    frame #9: 0x00007fff6fc71415 libsystem_pthread.dylib`thread_start + 13
  thread #9, name = 'Thread Pool Worker'
    frame #0: 0x00007fff6fbb81ce libsystem_kernel.dylib`semaphore_timedwait_trap + 10
    frame #1: 0x00000001009e123d mono`worker_thread [inlined] mono_os_sem_timedwait(flags=MONO_SEM_FLAGS_ALERTABLE) at mono-os-semaphore.h:124 [opt]
    frame #2: 0x00000001009e11bf mono`worker_thread at mono-coop-semaphore.h:57 [opt]
    frame #3: 0x00000001009e11a5 mono`worker_thread at threadpool-worker-default.c:391 [opt]
    frame #4: 0x00000001009e10b1 mono`worker_thread(unused=<unavailable>) at threadpool-worker-default.c:490 [opt]
    frame #5: 0x0000000100a93c73 mono`start_wrapper [inlined] start_wrapper_internal at threads.c:1151 [opt]
    frame #6: 0x0000000100a93be3 mono`start_wrapper(data=0x00007fc99c440890) at threads.c:1211 [opt]
    frame #7: 0x00007fff6fc72305 libsystem_pthread.dylib`_pthread_body + 126
    frame #8: 0x00007fff6fc7526f libsystem_pthread.dylib`_pthread_start + 70
    frame #9: 0x00007fff6fc71415 libsystem_pthread.dylib`thread_start + 13
(lldb) detach

=================================================================
Got a SIGSEGV while executing native code. This usually indicates
a fatal error in the mono runtime or one of the native libraries 
used by your application.
=================================================================

Abort trap: 6
Process 20055 detached
(lldb) quit
```

# 前提情報
・Fiddlerは下記サイトから入手
　https://www.telerik.com/download/fiddler
（バージョン：v4.6.20171.26113 beta）

・Mono Frameworkは下記サイトから入手
　channelは「Stable channel」を選択する。
　（「Visual Studio channel」では別のエラーが発生して起動できませんでした。）
　https://www.mono-project.com/download/stable/
<img width="968" alt="スクリーンショット 2019-01-06 13.26.36.png" src="https://qiita-image-store.s3.amazonaws.com/0/319350/be0b56f4-66a4-97f8-e036-acf6c969d963.png">


# 解決方法
「mono Fiddler.exe」ではなく、「mono --arch=32 Fiddler.exe」で起動する。
「--arch=32」をつけない場合はMono64bit版で起動されるが、これはWinFormsをサポートしていないらしい...

```Bash:Fiddler起動コマンド
mono --arch=32 Fiddler.exe
```