I have a Rev B iMac G5 and when my wife was working on it (using TexEdit) it randomly shut down lossing all power. The external speakers did not loose power. After wainting about 5-10 minutes my wife turned it back on and continued working in TexEdit when the computer lost power and shut off again. Is this serious and should I call apple care or take it in to the genuis bar? Thanks for giving any advice or tips.