Hi,We've got a couple of GXP2000 IP phones with some of them randomly hanging up calls. We have:Product Model:   GXP2000 (HW1.2B)Software Version:   Program-- 1.1.6.16    Bootloader-- 1.1.6.5SIP Server: Asterisk 1.4Trunk: ISDN BRI (Digium B410P)Symptom: During the call, the SIP (always the SIP side) will disappear. The remote party eventually hang up when no one responds.Logs:syslog dumps the following from the phone at the time the SIP device disapears:Nov 3 12:07:29 GS_LOG: [000][9620000512B][01010610] 2008-11-03 12:07:28 [Status]-ON HOOKAt the moment I don't have SIP debugging in Asterisk so no further details.Any ideas on what is causing this?Carel