[Atrix 4G Q&A, Help & Troubleshooting] ja450n:
Too new to post in the dev forums, but i wanted to post my experience with the Webtop Mod (http://xdaforums.com/showthread.php?t=980193) specifically using the 4.5.91 files downloaded from (http://xdaforums.com/showpost.php?p=15881436&postcount=834) in case any others are having this issue, and maybe to get some feedback from the mod devs, as I'd like to use this mod on my phone.

I noticed after replacing the stock APKs i started getting FC's when making and receiving phone calls, after pulling a logcat log from my phone, it seems the modded PortalApp.apk is at fault (log snippet below) i reverted to the stock PortalApp.apk and phone calls started working again.

09-07 18:42:15.665 1672 3590 I ActivityManager: Starting: Intent { act=android.intent.action.CALL dat=tel:xxx-xxx-xxxx flg=0x10000000 cmp=com.android.phone/.InCallScreen (has extras) } from pid 8281
09-07 18:42:16.615 3086 3086 D StatusBarService: enter playAnimationStatusBar, enable = false
09-07 18:42:16.635 1672 3007 D InputManager: phone state:2
09-07 18:42:16.995 8281 8281 E AndroidRuntime: FATAL EXCEPTION: main
09-07 18:42:16.995 8281 8281 E AndroidRuntime: java.lang.RuntimeException: Unable to instantiate receiver com.android.portal.IntentProxyReceiverForCallState: java.lang.ClassNotFoundException: com.android.portal.IntentProxyReceiverForCallState in loader dalvik.system.PathClassLoader[/system/framework/com.motorola.android.iextdispservice.jar:/system/framework/com.motorola.android.imirrorservice.jar:/system/app/PortalApp.apk]
09-07 18:42:16.995 8281 8281 E AndroidRuntime:	at android.app.ActivityThread.handleReceiver(ActivityThread.java:1826)
09-07 18:42:16.995 8281 8281 E AndroidRuntime:	at android.app.ActivityThread.access$2400(ActivityThread.java:124)
09-07 18:42:16.995 8281 8281 E AndroidRuntime:	at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1018)
09-07 18:42:16.995 8281 8281 E AndroidRuntime:	at android.os.Handler.dispatchMessage(Handler.java:99)
09-07 18:42:16.995 8281 8281 E AndroidRuntime:	at android.os.Looper.loop(Looper.java:130)
09-07 18:42:16.995 8281 8281 E AndroidRuntime:	at android.app.ActivityThread.main(ActivityThread.java:3806)
09-07 18:42:16.995 8281 8281 E AndroidRuntime:	at java.lang.reflect.Method.invokeNative(Native Method)
09-07 18:42:16.995 8281 8281 E AndroidRuntime:	at java.lang.reflect.Method.invoke(Method.java:507)
09-07 18:42:16.995 8281 8281 E AndroidRuntime:	at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
09-07 18:42:16.995 8281 8281 E AndroidRuntime:	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
09-07 18:42:16.995 8281 8281 E AndroidRuntime:	at dalvik.system.NativeStart.main(Native Method)
09-07 18:42:16.995 8281 8281 E AndroidRuntime: Caused by: java.lang.ClassNotFoundException: com.android.portal.IntentProxyReceiverForCallState in loader dalvik.system.PathClassLoader[/system/framework/com.motorola.android.iextdispservice.jar:/system/framework/com.motorola.android.imirrorservice.jar:/system/app/PortalApp.apk]
09-07 18:42:16.995 8281 8281 E AndroidRuntime:	at dalvik.system.PathClassLoader.findClass(PathClassLoader.java:240)
09-07 18:42:16.995 8281 8281 E AndroidRuntime:	at java.lang.ClassLoader.loadClass(ClassLoader.java:551)
09-07 18:42:16.995 8281 8281 E AndroidRuntime:	at java.lang.ClassLoader.loadClass(ClassLoader.java:511)
09-07 18:42:16.995 8281 8281 E AndroidRuntime:	at android.app.ActivityThread.handleReceiver(ActivityThread.java:1817)
09-07 18:42:16.995 8281 8281 E AndroidRuntime:	... 10 more
09-07 18:42:17.015 1672 3590 W ActivityManager: Process com.android.phone has crashed too many times: killing!