everything runes fine:
Thread 6 (Thread 0xb6a87b90 (LWP 32151)):
#0  0xb7f1e424 in __kernel_vsyscall ()
#1  0xb7cf6e67 in poll () from /lib/i686/cmov/libc.so.6
#2  0x08109d7b in ast_io_wait (ioc=0xb72ce938, howlong=2) at io.c:275
#3  0xb74f3bd5 in do_monitor (data=0x0) at chan_sip.c:22579
#4  0x0819274f in dummy_start (data=0xb60056c8) at utils.c:968
#5  0xb7ad14c0 in start_thread () from /lib/i686/cmov/libpthread.so.0
#6  0xb7d016de in clone () from /lib/i686/cmov/libc.so.6
---------------
the problem starts
Thread 6 (Thread 0xb6a87b90 (LWP 32151)):
#0  0xb7ad400f in __pthread_mutex_unlock_usercnt () from /lib/i686/cmov/libpthread.so.0
#1  0xb7d3bc0a in dl_iterate_phdr () from /lib/i686/cmov/libc.so.6
#2  0xb7d3ef65 in _Unwind_Find_FDE () from /lib/i686/cmov/libc.so.6
#3  0xb7a4219e in ?? () from /lib/libgcc_s.so.1
#4  0xb7a42a55 in ?? () from /lib/libgcc_s.so.1
#5  0xb7a42bc1 in _Unwind_Backtrace () from /lib/libgcc_s.so.1
#6  0xb7d16d28 in backtrace () from /lib/i686/cmov/libc.so.6
#7  0x08114a1f in ast_bt_get_addresses (bt=0x94e933c) at logger.c:1203
#8  0x08088b6c in __ast_pthread_mutex_trylock (filename=0xb7509b54 "chan_sip.c", lineno=15068, func=0xb75130f0 "dialog_needdestroy",
    mutex_name=0xb7509c20 "dialog", t=0x94e9298) at /usr/src/asterisk-1.6.2.10/include/asterisk/lock.h:630
#9  0x08088d7e in ?? ()
#10 0xb74cfed2 in dialog_needdestroy (dialogobj=0x94e98d0, arg=0xb6a87338, flags=7) at chan_sip.c:15068
#11 0x08089f00 in __ao2_callback (c=0xb72d8d00, flags=7, cb_fn=0xb74cfe83, arg=0xb6a87338, data=0x0, type=DEFAULT, tag=0x0, file=0x0, line=0, funcname=0x0)
    at astobj2.c:712
#12 0x0808a218 in ?? ()
#13 0xb74f3b94 in do_monitor (data=0x0) at chan_sip.c:22561
#14 0x0819274f in dummy_start (data=0xb60056c8) at utils.c:968
#15 0xb7ad14c0 in start_thread () from /lib/i686/cmov/libpthread.so.0
#16 0xb7d016de in clone () from /lib/i686/cmov/libc.so.6
----------------------
the problem is still there
Thread 6 (Thread 0xb6a87b90 (LWP 32151)):
#0  0xb7d3d5ca in ?? () from /lib/i686/cmov/libc.so.6
#1  0x00000028 in ?? ()
#2  0xb6a85e48 in ?? ()
#3  0x000000c7 in ?? ()
#4  0x00000000 in ?? ()
-----------------------
everything is fine again
Thread 6 (Thread 0xb6a87b90 (LWP 32151)):
#0  0xb7f1e424 in __kernel_vsyscall ()
#1  0xb7cf6e67 in poll () from /lib/i686/cmov/libc.so.6
#2  0x08109d7b in ast_io_wait (ioc=0xb72ce938, howlong=19) at io.c:275
#3  0xb74f3bd5 in do_monitor (data=0x0) at chan_sip.c:22579
#4  0x0819274f in dummy_start (data=0xb60056c8) at utils.c:968
#5  0xb7ad14c0 in start_thread () from /lib/i686/cmov/libpthread.so.0
#6  0xb7d016de in clone () from /lib/i686/cmov/libc.so.6