So my iMac 27" just made a really loud noise while playing music using pandora app. It's tough to describe almost like a power surge to an amp when you shut it down mid riff. I had installed 8gb additional ram about 2 weeks ago. Hope that's not what caused it. It's been running fine until I updated the adobe air because the pop-up said to for the pandora app. Now I can't even get it to startup properly. The one time it did start all the way up I tried to use time machine to undo the update hoping that would fix issue and Mac just shut down ( powering off not just sleep). Now the Mac freezes on the white screen with the apple. I know this might be hard to understand but I'm not a computer genius so it's tough for me to explain. Any help or suggestions? If I can't figure it out today, I'm bringing it in to the Genius Bar. Thanks. Running current version of ML. 12gb ram total. I think it's the i5 chip. 1TB hd about 1/2 full. Mid 2010 model.