The freeswitch log show this before it hits my hangup hook in lua.  I don't have a pcap trace of the sip messaging, I can try that tonight, it would definitely show where the hangup is coming from.  I'm recording to a local disk as a .ul file, so a headerless ulaw format. 

2009-06-08 21:25:44 [DEBUG] sofia.c:3037 sofia_handle_sip_i_state() Channel sofia/external/5555551212@192.168.3.21 entering state [terminated][200]
2009-06-08 21:25:44 [NOTICE] sofia.c:3597 sofia_handle_sip_i_state() Hangup sofia/external/5555551212@192.168.3.21 [CS_EXECUTE] [NORMAL_CLEARING]
2009-06-08 21:25:44 [DEBUG] switch_channel.c:1660 switch_channel_perform_hangup() Send signal sofia/external/5555551212@192.168.3.21 [KILL]
2009-06-08 21:25:44 [DEBUG] switch_core_session.c:933 switch_core_session_signal_state_change() Send signal sofia/external/5555551212@192.168.3.21 [BREAK]
2009-06-08 21:25:44 [DEBUG] switch_core_codec.c:122 switch_core_session_set_read_codec() Restore original codec.
2009-06-08 21:25:44 [NOTICE] switch_cpp.cpp:1122 console_log() hangupHook: 272423 status: hangup



Thanks
D-