I had an Intertel tech. look at it last week and he couldn't find anything wrong...aside from us not getting name and number caller ID with our PRI/PAL ...which no one has ever been able to figure out (we just get number).
After the tech. left the system again went down (reset). I took a deep breath and made sure there were no baseball bats handy. I removed the phone system from the UPS we had it on. I think that must have been the problem. It's odd, because I have a PC attached to that UPS as well and it never goes down when the phone system does. But, I'm going to see how things go. If the system is up for two weeks straight, I'm going to conclude that it was the UPS causing the issue and I'll likely replace it. Why a UPS would cause the dial tone issues... I have no idea. I suppose it could have been underpowered or some such, or the resets were causing the PBX to not always come back up correctly. In any event, it will sometimes take a week before the resets start happening... so, I think two weeks is a good litmus.
Thanks to everyone who took the time to help with this issue. I learned a lot. I will post back after another week to let everyone know whether or not the resets continued. In the meantime, I procured a replacement power supply and CPU card... so, I think I'm pretty well covered if it turns out not to be environmental.
