We have about 12 of the older 7920 phones. They have been working fine. We are trying out two 7921G phone with 33 more to be deployed. But the new 7921G phones are giving us a Network busy when a call tries to connect or when you try and call out. The phone appears to be registered fine. But an incomming call will ring once, flash the persions caller ID then drop the call and show a "Network Busy" Error. What can I try? I have 1200AP's. Scattared throught our plant.