Cisco 7940 & "Phone Locking"

Used to be running a trixbox system with a host of Cisco 7940’s. Recently upgraded them to AsteriskNow/FreePBX.

Several users are in a queue. When the phones ring (this is a call center so it’s non-stop), the phones “lock” and do not allow you to interact with them to dial out, anything. This is a problem that started happening since the upgrade; I’ve copied the phone config from the /tftpboot folder on the original machine (SIPDefault.cnf) and applied it to the phones in question, but it doesn’t seem to have made a difference. I went line by line through the queue setup to see if I could find some differences, and I cannot. At first I thought I might be looking for “skip busy agent” but the problem isn’t when the phones are in use, it’s when they’re not in use, the phone rings, and the caller wishes to use the phone afterwards; or, if a user is in the middle of dialing, they’ll be kicked out of the dialer and have to wait until someone picks up.

What could cause this behavior? Where should I be looking? I don’t think it’s with the phones, as they’re set up the same as before, so I’m thinking it has to be on the PBX side.

Has no one experienced this before?