[jtroutma]

One other possiblity:
Is this UPS that you are using a smart monitoring unit attached to your system? If it is, the software controlling the unit MIGHT be wigging out. Happened to me with a server here at work. The UPS was causing the system to have a problem which in turned caused the UPS to have an even bigger problem.

Try running that UPS on another elecrical appliance with a similar load that the computer attached to it before was using. Say like a halogen lamp or something. If the UPS wigs out on that, then it is a UPS failure. If not, then it might be a software problem.

Also, if you need to, I know a company that you can ship your UPS to and they will completely refurbish the whole unit, replace batteries, and warranty the unit for 3 years.

good luck.