Hi Gerry, and welcome to the VMware Communities!
Which version of gdb are you running?
If it's an Apple build of gdb, try launching gdb with -arch x86_64 as a command-line argument.
Either way, try an explicit set arch i386:x86-64 ... for some versions of gdb, that seems to be necessary to really kick it into 64-bit mode, even if show arch reports that it is already set to i386:x86-64.
Cheers,
--
Darius