Computer hibernating at strange times

Win 7 x64 SP1. ASUS A8N5X motherboard with an Athalon 64 X2 processor.

I have my hibernation timer set to 45 minutes of inactivity or if my UPS battery level drops below 50%.

For the past week or so, I'll leave my computer to get a snack or something and when I come back it has started hibernating. I restart the computer and it tells me that it shut down because battery levels are low.

There are no power glitches. No alarms from the UPS and the battery monitor shows that the battery is charged.

One thing did just occur to me. This all started after we had a major thunderstorm with a power failure which prompted an automatic shutdown. Is there a flag that didn't get reset?

Thoughts?

Thanks.

Still happening. Went to the kitchen to get a cup of coffee and when I came back, the computer was off.

Set the inactivity time to 1 minute and watch it go into hibernation...

Then wake it up and set it back to 45 minutes.

I'm thinking that the problem has something to do with my UPS. I unplugged the UPS's USB cable and the problem vanished.

Are you using W7 to watch the UPS levels or a 3rd party app?

I'm letting Win 7 do it.

Does W7 report that the battery is at 100%?

What is the manuf/model of the UPS?

UsernameIssues said:

Does W7 report that the battery is at 100%?

What is the manuf/model of the UPS?

Yep, 100%. APC Smart-UPS Pro 500.

That particular APC model is not meant for use with a Power Factor Corrected (PFC) computer supply.

See this PDF.

Oh wow. This is really getting complicated.

In words of one syllable, why would that cause my computer to hibernate?