That sucks. Gosh darn power supplies are always crapping out. Most common piece of hardware to fail for sure.
I've been using my laptop at home for months because AlexCCCP is too lazy to help me fix the computer he built for me
Don't trust it. That's usually a sign of half-dead capacitors, or other internal components failing, within the power supply. It failed once, anticipate that it *WILL* fail again, and get your replacement on hand and on deck.