Nope, F5 seemed to work for me (well, actually, fn+F5 since I'm on a Titanium PowerBook. Unmodifed F5 just turns up the volume on the speakers). Thanks for the tip on the text encoding, though; that did the trick.
I've dropped the CPU cycles to 20-60, and I still have the same problem, although now it occasionally prints out the following lines after the "SDL parachute" deploys:
dosbox(26160,0xa000ef98) malloc: *** Deallocation of a pointer not malloced: 0x3538e50; This could be a double free(), or free() called with the middle of an allocated block; Try setting environment variable MallocHelp to see tools to help debug
dosbox(26160,0xa000ef98) malloc: *** error for object 0x35340f0: double free
dosbox(26160,0xa000ef98) malloc: *** set a breakpoint in szone_error to debug
After that, it gives me a command prompt (instead of freezing and requring a Ctrl^C). Unfortunately, still no debug file.
Would it be helpful at all if I ran GDB on dosbox and sent you a copy of the backtrace when it segfaults?