#3 Register Error w/Uniden UIP200

We changed our office IP networks from the network to the network.

We re-addressed everything and now our Uniden UIP200 phones will give us a register error several times/day. The phones still work for out-bound calls, but it is as if the PBX looses the phone.

Anyone have any ideas?

Did you change anything else? Switches routers hubs?

They are all the same.