Strange Mozilla crash

[Daniela]

Hi!

My Mozilla hangs very often, and now I attached to the hanged process with gdb 
to see what's wrong. I have debug symbols in Mozilla, in every other program 
and in the entire OS. The backtrace is:

#0  0x28458d60 in __sys_poll () from /usr/lib/libc_r.so.4
#1  0x284582ac in thread_kern_poll (wait_reqd=1)
    at /usr/src/lib/libc_r/uthread/uthread_kern.c:817
#2  0x28457c71 in _thread_kern_scheduler ()
    at /usr/src/lib/libc_r/uthread/uthread_kern.c:493
#3  0x0 in ?? ()

When detaching from the program, I see the following:
The program is running.  Quit anyway (and detach it)? (y or n) y
Detaching from program: /usr/ports/www/mozilla/work/mozilla/dist/bin/
mozilla-bin, process 33788, thread 1
ptrace: No such process

But the process is still there, so I don't know why ptrace can't find it.
What can I do now? I'm really curious what goes on in a hanging program, and 
maybe I can even fix a bug. I'm familiar with assembly language and also have 
basic C knowledge.

Regards,
Daniela