First: how old is your neighborhood? Was it built in the past 20 years, or is it 300 years old, with electricity from the early 1900's? Is your service sufficient for your computers load? (Wattage/Voltage=Amps)

Second: it sounds like your neighborhood has a bad transformer. Check with your neighbors, and/or test their power to see if it is as bad as yours. I'd report it to your power company.