I would not place much faith in this particular backtrace; gdb is badly broken on SL and Lion, it gets seriously mucked up by the way shared library stubs work (probably among other issues, but this one was easy to spot:  just try to trace through such a call), and I get failures running stuff in gdb that do not happen outside of it.  Backtraces from core files are okay, but running something inside gdb will often fail in quasi-random places.

(there's a bug open in MacPorts about it.  someone did manage to get the very latest gdb to work at one point, but both Apple's and MacPorts' gdbs are known to fail.)