I've been having this same issue for the last 6 months. I have 2 IPRC's, one on a DMZ for off-site phones and one on the LAN which my branch office connects to via a MPLS VPN T1 line with 7 phones, I have an IP phone in the office with the IPRC, and i have one user on an IP phone with a Sonicwall to Sonicwall VPN setup via the public internet.

Now that you know the setup:

I've swapped the IPRCs since the office phones are much more important then any off-site phone. This worked for the short term but today it started again. I've verified that the networks are staying up so it's an IPRC issue.

I was going to start with new Firmware on everything, but i don't know where to get it.

Does anyone thing this will help my issue? Any advice where to get the newest firmware. My phones are 8620s and current version is 1.02 i believe.

Thanks!
Andy