I'm debugging a core file.  Upon trying to do a backtrace, I get:

<snip>
(gdb) bt
#0  0x001a2f68 in segv_handler (signo=<value optimized out>) at /builds/Trunk-Worldbuild/latest/svn/lib/io-pkt/sys/main.
c:500
#1  <signal handler called>
../../gdb/frame.c:767: internal-error: frame_register_unwind: Assertion `value != NULL' failed.
A problem internal to GDB has been detected,
further debugging may prove unreliable.
</snip>

My GDB version is:
GNU gdb (GDB) 7.1 EXPERIMENTAL (rev. 545)

Thanks