I have problems getting my SIP Phone 3911 :s to register with my Call Manager 6.0.1. Sometimes they register and sometimes not. If the manage to register they unregister shortly. While registered they behave strange, calls are not working properly. Also, they don't upgrade with the new software. Th phones are running SIP3951.8-1-1-4, we have SIP3911_3951.8-1-2. Any ideas someone ?