[Desire Q&A, Help & Troubleshooting] /rant/:
This thread can be closed. I fixed the problem by restoring the data from my stock ROM, then flashing the 2.29.405.5 update.

So, after flashing LeeDroid, everything seemed fine. I installed a bunch of apps to my ext3-partition and it was damn fast.

Now, for some reason WhatsApp suddenly won't work anymore (two hours ago, it was doing just fine). I have a logcat here:

I/DEBUG ( 836): *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***
I/DEBUG ( 836): Build fingerprint: 'htc_wwe/htc_bravo/bravo/bravo:2.2/FRF91/263770:user/release-keys'
I/DEBUG ( 836): pid: 1498, tid: 1498 >>> com.whatsapp <<<
I/DEBUG ( 836): signal 11 (SIGSEGV), fault addr 422cddb4
I/DEBUG ( 836): r0 00000005 r1 0000441f r2 422bcd38 r3 00000000
I/DEBUG ( 836): r4 4295fffe r5 42093b80 r6 bef8c4f0 r7 000007f9
I/DEBUG ( 836): r8 80817200 r9 4295fff4 10 00000000 fp bef8c798
I/DEBUG ( 836): ip 000000f9 sp bef8c4a8 lr 8081bff0 pc 8081b060 cpsr 20000010
I/DEBUG ( 836): d0 6472656767756265 d1 0a3d3d3d3d203036
I/DEBUG ( 836): d2 676f6c203d3d3d3d d3 76656c20656c6966
I/DEBUG ( 836): d4 42096f9c42096f68 d5 420a5e9042096fd0
I/DEBUG ( 836): d6 420a5ef8420a5ec4 d7 3eaaaaab3f800000
I/DEBUG ( 836): d8 0000000000000000 d9 0000000000000000
I/DEBUG ( 836): d10 0000000000000000 d11 0000000000000000
I/DEBUG ( 836): d12 0000000000000000 d13 0000000000000000
I/DEBUG ( 836): d14 0000000000000000 d15 0000000000000000
I/DEBUG ( 836): d16 0027e428bef8c280 d17 4082f00000000000
I/DEBUG ( 836): d18 42eccefa43de3400 d19 3fe00000000000b4
I/DEBUG ( 836): d20 4008000000000000 d21 3fd99a27ad32ddf5
I/DEBUG ( 836): d22 3fd24998d6307188 d23 3fcc7288e957b53b
I/DEBUG ( 836): d24 3fc74721cad6b0ed d25 3fc39a09d078c69f
I/DEBUG ( 836): d26 0000000000000000 d27 0000000000000000
I/DEBUG ( 836): d28 0000000000000000 d29 0000000000000000
I/DEBUG ( 836): d30 0000000000000000 d31 0000000000000000
I/DEBUG ( 836): scr 80000012
I/DEBUG ( 836):
I/DEBUG ( 836): #00 pc 0001b060 /system/lib/libdvm.so
I/DEBUG ( 836): #01 pc 00022c04 /system/lib/libdvm.so
I/DEBUG ( 836): #02 pc 00021aa0 /system/lib/libdvm.so
I/DEBUG ( 836): #03 pc 0005d162 /system/lib/libdvm.so
I/DEBUG ( 836): #04 pc 000659ec /system/lib/libdvm.so
I/DEBUG ( 836): #05 pc 0001bfa0 /system/lib/libdvm.so
I/DEBUG ( 836): #06 pc 00022c04 /system/lib/libdvm.so
I/DEBUG ( 836): #07 pc 00021aa0 /system/lib/libdvm.so
I/DEBUG ( 836): #08 pc 0005cfa0 /system/lib/libdvm.so
I/DEBUG ( 836): #09 pc 000480fe /system/lib/libdvm.so
I/DEBUG ( 836): #10 pc 0002ffbc /system/lib/libandroid_runtime.so
I/DEBUG ( 836): #11 pc 000310b8 /system/lib/libandroid_runtime.so
I/DEBUG ( 836): #12 pc 00008ca8 /system/bin/app_process
I/DEBUG ( 836): #13 pc 0000d430 /system/lib/libc.so
I/DEBUG ( 836):
I/DEBUG ( 836): code around pc:
I/DEBUG ( 836): 8081b040 e1d430b4 e1d410b2 e7952103 e3520000
I/DEBUG ( 836): 8081b050 0a000457 e5922000 e5922074 e5054008
I/DEBUG ( 836): 8081b060 e7920101 eb000378 e320f000 e320f000
I/DEBUG ( 836): 8081b070 e320f000 e320f000 e320f000 e320f000
I/DEBUG ( 836): 8081b080 e1d4a0b4 e5962010 e20aa00f e1d410b2
I/DEBUG ( 836):
I/DEBUG ( 836): code around lr:
I/DEBUG ( 836): 8081bfd0 e088f30c e1a01000 e5960018 fa010189
I/DEBUG ( 836): 8081bfe0 ea00001a e3a00001 e3a09000 ebffff7d
I/DEBUG ( 836): 8081bff0 e2450014 e5905000 e5909004 e515200c
I/DEBUG ( 836): 8081c000 e5963018 e3520000 1592a000 e3a01000
I/DEBUG ( 836): 8081c010 0affff8a e1f970b6 e5862010 e59a1028
I/DEBUG ( 836):
I/DEBUG ( 836): stack:
I/DEBUG ( 836): bef8c468 40025ae0 /dev/ashmem/mspace/dalvik-heap/zygote/0 (deleted)
I/DEBUG ( 836): bef8c46c 808659f1 /system/lib/libdvm.so
I/DEBUG ( 836): bef8c470 4001d2a0 /dev/ashmem/mspace/dalvik-heap/zygote/0 (deleted)
I/DEBUG ( 836): bef8c474 00000001
I/DEBUG ( 836): bef8c478 428bd2d0 /system/sd/dalvik-cache/system@framework@core.jar@classes.dex
I/DEBUG ( 836): bef8c47c 00000001
I/DEBUG ( 836): bef8c480 4001d2a0 /dev/ashmem/mspace/dalvik-heap/zygote/0 (deleted)
I/DEBUG ( 836): bef8c484 40020c18 /dev/ashmem/mspace/dalvik-heap/zygote/0 (deleted)
I/DEBUG ( 836): bef8c488 47949618 /dev/ashmem/mspace/dalvik-heap/2 (deleted)
I/DEBUG ( 836): bef8c48c bef8c4f8 [stack]
I/DEBUG ( 836): bef8c490 0000054d
I/DEBUG ( 836): bef8c494 428979b8 /system/sd/dalvik-cache/system@framework@core.jar@classes.dex
I/DEBUG ( 836): bef8c498 42093b10
I/DEBUG ( 836): bef8c49c bef8c4f0 [stack]
I/DEBUG ( 836): bef8c4a0 df002777
I/DEBUG ( 836): bef8c4a4 e3a070ad
I/DEBUG ( 836): #00 bef8c4a8 0000000f
I/DEBUG ( 836): bef8c4ac bef8c4f0 [stack]
I/DEBUG ( 836): bef8c4b0 00000000
I/DEBUG ( 836): bef8c4b4 0000cd88 [heap]
I/DEBUG ( 836): bef8c4b8 00036348 [heap]
I/DEBUG ( 836): bef8c4bc 000003a4
I/DEBUG ( 836): bef8c4c0 808a3334 /system/lib/libdvm.so
I/DEBUG ( 836): bef8c4c4 808a7f50 /system/lib/libdvm.so
I/DEBUG ( 836): bef8c4c8 bef8c798 [stack]
I/DEBUG ( 836): bef8c4cc 80822c08 /system/lib/libdvm.so
I/DEBUG ( 836): #01 bef8c4d0 0000cd80 [heap]
I/DEBUG ( 836): bef8c4d4 bef8c4f0 [stack]
I/DEBUG ( 836): bef8c4d8 80822b88 /system/lib/libdvm.so
I/DEBUG ( 836): bef8c4dc 00000000
I/DEBUG ( 836): bef8c4e0 000003a4
I/DEBUG ( 836): bef8c4e4 80821aa4 /system/lib/libdvm.so
E/ActivityManager( 167): fail to set top app changed!
D/Zygote ( 140): Process 1498 terminated by signal (11)

As it says: signal 11 (SIGSEGV), fault addr 422cddb4. When I want to run WhatsApp, I get a dark screen like it was really starting - but then it returns straight to my desktop. What is wrong?

I've already checked the ext3-partition for errors and cleared caches.