You can type "bt" in gdb and walk the stack to see where it is bombing out.  For QT wallet, you will need to add a few flags in the .pro file first so you get the symbols in the debugger.

QMAKE_CXXFLAGS_RELEASE += -g
QMAKE_CFLAGS_RELEASE += -g
QMAKE_LFLAGS_RELEASE += -g

Put that in your .pro file, recompile, and run with gdb, and then walk the stack and find the method where it is segfaulting (each time you use the bt command it will walk a frame).