Hi, I am using PJSIP release 1.0rc2 with our sip phone application on Win XP and Vista. Everything works fine on WinXP but I am facing some "freeze" issues on Vista. PJSIP seems to "freeze" on Vista and this always seems to happen while acquiring the pjsua global mutex. Here's the call stack of one such "freeze" - sipPhone.dll!pj_mutex_lock(pj_mutex_t * mutex=0x00bdf31c) Line 925 C sipPhone.dll!pjsua_acc_get_info(int acc_id=0, pjsua_acc_info * info=0x0261f270) Line 1285 + 0xb bytes C sipPhone.dll!sipPhone::UnRegisterLine(int hLine=6) Line 4097 + 0x19 bytes C++ I couldn't find anything similar to this reported/fixed on pjsip ticket list. I am trying to figure out more using windbg but have been unable to make it work on Vista. Will post more information if I get any. Suggestion are welcome. Thanks, Anshuman