So earlier tonight my 27" iMac (2009) went pixilated (green, yellow, blue, white small pixels) then the screen went black, but the computer was still running. I shut it down and turned it back on and I didn't have a problem until recently. After clicking play on a video on Facebook, the pixels returned and the screen went black again. I then proceeded to shut the computer down, but when I turned it back on, this is what I saw (refer to picture, sorry it's upsidedown)
The lines eventually disappeared along with the Apple logo, but the screen remained white for at least five minutes. I restarted my mac again, but the lines returned and the screen stayed white. That was around ten minutes ago and the screen is still white. What's wrong here?
Also, I recently upgraded to Mountain Lion about two months or so ago from Snow Leopard (either 10.8 or 10.8.1) if that's important at all.