debug of multithreaded program turns to be impossible during execution

Hello,

I'm debugging a multithreaded program using GDB. Various threads are created and exit during execution. GDB copes successfully with the multiple threads (e.g. 'thread apply 3 bt' reports successfully backtrace of thread 3), but then at one point loses control of the program:

(gdb) c
Continuing.
[New Thread 0x41401940 (LWP 13370)]
 [Thread 0x40a00940 (LWP 13333) exited]
[New Thread 0x41e02940 (LWP 13371)]
...
[New Thread 0x45a08940 (LWP 13377)]
[New Thread 0x46409940 (LWP 13378)]
 [Thread 0x41e02940 (LWP 13371) exited]
 [Switching to Thread 0x45a08940 (LWP 13377)]
Cannot remove breakpoints because program is no longer writable.
Further execution is probably impossible.
0x00002aaaab98348f in start_thread () from /lib64/libpthread.so.0
ptrace: No such process.

Surprisingly, although debugging is no more possible, the program is not dead:

(gdb) q
A debugging session is active.

        Inferior 1 [process 13296] will be killed.

Quit anyway? (y or n) y
[Thread 0x46409940 (LWP 13378) exited]
[Thread 0x45a08940 (LWP 13377) exited]
...
[Thread 0x2aaaaccbe580 (LWP 13296) exited]

Some details:
GDB version: 7.6
OS: RHEL 5.1 based
GLIBC: glibc-2.5-18
/lib64/libthread-1.0.so is not stripped.

Your assistance will be appreciated.
Thanks,
Avi