I just bought a new UPS. Now since I started using it I experienced at least 3 random freeze in Windows 7 and it happens during the first 10 minutes of start-up. Note when I say freeze, I mean I literally can't do anything in Windows, everything is frozen including the mouse cursor.
Is it possible that I bought a broken or underpowered UPS? Can an underpowered UPS make a computer freeze?
BTW, this power calculator says I'm under 300W, but I do have 500W PSU.
Update: FEB 9, 2012
I have replaced my APC UPS with another brand: FSP UPS which is the same brand with my PSU. It's been running with no problem for the last 5 days.
In reference to my answer below: Could it be really true that non-SmartUPS APC models are not compatible with active PFC PSUs? I find it hard to believe since most branded PSUs are active PFC.