1. Start Virtual AGC in debug mode: yaAGC --core=Colossus249.bin --cfg=CM.ini --debug
2. Try to examine register A with command "x A". The yaAGC immediately quits with segmentation fault. "x 0" or "x L" or "x 1" also result in segfault.

I've built my yaAGC from source yaAGC-dev-20100220.tar.bz2, op.system is Debian/Lenny

Seem to me the reason for this behaviour is an unhandled nullification of a string variable at agc_gdbmi.c:1709
if ((s = strstr(s,"/"))) which ends up in a segmentation fault at agc_gdbmi.c:1716, where the variable "s" is referred.