(gdb) bt
#0  0xb73afa8b in close_mailbox (vms=0xb6c36788, vmu=0xb6c36284)
    at app_voicemail.c:4836
#1  0xb73b694c in vm_execmain (chan=0x820abf8, data=0xb6c3d008)
    at app_voicemail.c:6743
#2  0x080b5ee1 in pbx_exec (c=0x820abf8, app=0x81d1ff8, data=0xb6c3d008)
    at pbx.c:532
#3  0x080b9327 in pbx_extension_helper (c=0x820abf8, con=0x0,
    context=0x820ad78 "sip-internal", exten=0x820adc8 "7777", priority=1,
    label=0x0, callerid=0x81dd048 "2400", action=E_SPAWN) at pbx.c:1833
#4  0x080ba3f5 in ast_spawn_extension (c=0x820abf8,
    context=0x820ad78 "sip-internal", exten=0x820adc8 "7777", priority=1,
    callerid=0x81dd048 "2400") at pbx.c:2288
#5  0x080ba8c5 in __ast_pbx_run (c=0x820abf8) at pbx.c:2388
#6  0x080bb61f in pbx_thread (data=0x820abf8) at pbx.c:2601
#7  0x080f50b9 in dummy_start (data=0x8180820) at utils.c:545
#8  0xb7f58240 in start_thread () from /lib/tls/i686/cmov/libpthread.so.0
#9  0xb7d833de in clone () from /lib/tls/i686/cmov/libc.so.6