Here's what I got after I typed bt:

-----------
Program received signal SIGABRT, Aborted.
0x0012d422 in __kernel_vsyscall ()
(gdb) bt
#0  0x0012d422 in __kernel_vsyscall ()
#1  0x01830651 in raise () from /lib/tls/i686/cmov/libc.so.6
#2  0x01833a82 in abort () from /lib/tls/i686/cmov/libc.so.6
#3  0x0178a52f in __gnu_cxx::__verbose_terminate_handler() ()
   from /usr/lib/libstdc++.so.6
#4  0x01788465 in ?? () from /usr/lib/libstdc++.so.6
#5  0x017884a2 in std::terminate() () from /usr/lib/libstdc++.so.6
#6  0x017885e1 in __cxa_throw () from /usr/lib/libstdc++.so.6
#7  0x001ac9b8 in gazebo::World::Fini (this=0x821f678)
    at
/opt/ros/cturtle/stacks/simulator_gazebo/gazebo/build/gazebo-r8905/server/World.cc:432
#8  0x001e9ed1 in gazebo::Simulator::Fini (this=0x81eac20)
    at
/opt/ros/cturtle/stacks/simulator_gazebo/gazebo/build/gazebo-r8905/server/Simulator.cc:394
#9  0x0811918a in main ()
----------------
Thanks!
-Gavin