I have 4 Polycom IP320 phones and a Linksys ATA that I'm having trouble with. The Polycom phones will register (to the PBX) and will stay registered. The Polycom will register, stay registered for a time (less than 5 minutes) and then lose registration. We are able to make outbound calls from them but not inbound. Still Googling now and will post if I'm able to resolve it (along with the resolution) but wanted to see if anyone else was having the same problem. I found one post where someone had had the problem but never saw a response.