Originally Posted by PavelT
interesting. so apple came to your house and fixed it and billed you?
My recommendation is to take it to a friend's house. It's really easy to put the iMac in the box, so just do that, bring it over to a bud's house, and make sure it's not something in your house. Honestly, if it does it at certain times of the day it's unquestionably a power-in-your-house/area issue. Now whether it's the iMac being sensitive to it or symptomatic of a bigger problem - I don't know. But now you know the issue, the question is what to do to address it.