Polycom BLF acting strangely - random "busy" state

Greetings all…

FreePBX 2.6, with Asterisk 1.6.0.15, all running on a Debian Lenny VMware ESX instance.

I’ve got 2 stations, a Polycom 650 and a 601. Each has a buddy watch set for the other station. I enabled the presence and messaging features in sip.cfg and rebooted the phones. At first, it works quite well. Make a call, the other station notices that you’re on the phone, just like you’d hope.

Here’s where it gets weird. After a seemingly random amount of time (anywhere from 30 seconds to 20 minutes, that I’ve observed), both stations show as “on the phone”, even though there are no calls in progress.

Calling from one station to the other and immediately hanging up sets it all right, until it happens again after an indeterminate amount of time…

Anyone encountered this before? Thanks…