It's likely the power supply dying. If it's worth your while- try another. Maybe a local shop will let you buy one to test & bring back if that isn't it (or test yours if you bring it in to them)...Pretty straightforward to replace.
answered Apr 26 '11 at 06:51
is this from a powered on or off state?
If the computer was on:
If the computer was off:
answered Jun 06 '10 at 08:11