Brain-storming:
What datatype is "ExitFadeCounter" (not that it should actually matter in this case)?
Slightly more "scientifically", looking at the address that it died at on my iPaq, it died in the process's DLL (mapping) space, not in the executable itself. Perhaps you're sending a bad parameter to a DLL function?
So:
Check that GetDisplay() is giving you a valid return?
Put an assert on ExitCounter to make sure that when you use it in DrawLine, it's not negative (in case something else has inadvertantly trashed it).
Your other "external" calls look "safe" (though I don't know the PocketFrog library).