I have one user with a Dell Vostro 220 desktop, that has an APC UPS 350 as their battery backup/surge protector, that will get pop up warning that battery is low & should switch to AC power. The computer will shutdown at that point, but will start back up no problem. THis was in a new building & AC outlet had checked out ok. I have also replaced the power supply, but the problem is still there. Even stranger is the fact that I replaced her computer with an older one I had back in the server room (optiplex 380, if it matters) & it has been ruing fine for a day now with no problems. I have her old computer in the server room & it has been running fine for a day. That might make me think it's in the UPS, but I have aleready replaced that once over the past couple of months.