(gdb) bt
#0  0xb7faf410 in __kernel_vsyscall ()
#1  0xb7dffb4e in __lll_mutex_lock_wait () from /lib/libpthread.so.0
#2  0xb7dfb9f8 in _L_mutex_lock_51 () from /lib/libpthread.so.0
#3  0xb7dfb41d in pthread_mutex_lock () from /lib/libpthread.so.0
#4  0xb7e2b042 in PR_Lock () from /usr/lib/libnspr4.so
#5  0xb7e8f72e in ?? () from /opt/mozilla/lib/firefox-2.0.0.6/libxpcom_core.so
#6  0x080dfba0 in ?? ()
#7  0x00000000 in ?? ()