I own a 7920, I have configured it properly. It receives inbound calls fine, however if I dial a number/extension and press Send. I immediatelly receive the "Network Busy" error message.
The disturbing thing is that if I press any of my speed dials the call is dialed with no issues.
I am usig the Cisco Linksys WRT610N wireless router. I also shutted sown all the wireless devices, thinking that the channel usage threashold would be high and causing the phone to fail but not even that made a difference