Screen Goes Black on the iMac

Hey All -

So I purchased my iMac I believe in late 2011, possibly early 2012.

Anyhew, the early Spring of 2013 my screen just went black while I was still working away on my computer. I was baffeled because the screen seemed to be off, but there was still music playing from my computer speakers. The only thing I could do to get it back on was to click the power button in the back to put it to sleep and then to wiggle the mouse to wake up the computer.

It ramdomly did this a few more times.

I checked to see if I had set up any hot keys or hot corners, I triple checked just to make sure I wasn't going crazy, and there was nothing set in my computer settings.

I thought, after reading some forums, that it was the fans, so I installed some app that allows one to control the fans on their computer. I'm not sure if this actually did the trick, but it didn't go black as often as it usually did. I also have a feeling that these incidents may be caused because of the screen brightness settings? Or not, who knows. I've also read it could be the logic board or video card.

Whatever it was, it stopped doing this. and would maybe randomly do it once a month. Until last night....cue scary music. It started doing it, and my screen would only stay on for 30 seconds and go black again (my music still playing on my speakers). Which is incrediably frustrating as I was trying to work. My computer is my livelyhood. As I am sure it is for a lot of people. So with that said....I'm slightly freaking out.

I'd take it into the genius bar, but I live in Boston and have no car, so I want to see if I can figure this out before hauling it over there and forking over a cold 1K to fix the **** thing.

Anyways, I'm not sure what to do. I'm not sure what's wrong with it, and am curious if other people have had this problem and have found a solution? Or have some suggestions. Any advice or help would be appreciated.

Cheers!

Tara