I have a couple of 7920 phones that keep re-registering with Call Manager. AP authentication and DHCP work fine. Once the phone comes up, it registers with CCM. I can place and receive calls on the phone. After a couple of minutes, the phone shows it is registering with CCM again. If I'm on a call, the call gets dropped and the phone shows 'Call Manager down'. The 7940 phones on the network are not having any issues.
We are using CCM 4.2(3) and the firmware on the phone is 7920.4.0-03-00.