Im hoping one of you really sharp fellas has some ideas for me. After a couple months we are at our end on this one; So we have a customer with 6 sites with IP office, using the Comcast's version of an MPLS network.(i forget the exact term they call it) So they each have a control unit running 8.1.xx, with about 10-15 phones at each site. Each site has a Sonicwall, all identical units as far as I know. Whats happening is that at random time frames, ranging from 1 day to 3 days between occurances, they lose the ability to 3-digit intercom dial from site to site. The IPO shows no errors, no alarms for the SCN, NOTHING. But they get a busy signal when they try to dial site to site using the "network". They also of course lose access to their mail server (VM pro) which is at what we will call the "Main" site. So basically they lose network connections. However, we see no errors as i said, AND we can "ping" from one Control unit to another, in any direction, any sites, and everyone "sees" each other, but no phone to phone intercom ability. But if we just restart the control unit at the main site, it starts working again just fine, for a random amount of time. last week it went 4 days just fine. then once it happened twice in one day. The IT tech for the client has spent countless hours wth Sonicwall support, Comcast support, etc. checking settings, etc. but no luck. We even resorted to switching out the two combo cards in that particular site to rule out a "glitch" in the VCM funstions of the module. We are going to switch out the entire control unit tomorrow. All of us including our programmer does not feel its an issue with the IPO or losin its network connections, because like I said, we can ping back and forth so the TCP seems fine when the 3-digit diaing is not working. Also whats strange is that none of the 6 sites can communicate but only resetting the "main" site fixes everything. Everyone we talk to says 'its the firewall"...but what??? And if it was a setting, either in the firewall or the IPO, the settings do not change so it would either always work or not. Its like it hits some sort of "threshold" then freezes up. I have no other clients using this Comcast type multi-site service to compare to. One last thing: in case it matters, they have a full PRI at the "main" site, and all the other sites are programmed to dial out THROUGH this site on thr PRI. each of smaller sites only has analog lines fro inbound only. So all of this outbound dialing ability lost during this issue....HELP!!!!