Downloaded ML last night, and things did not go well. I'm now stuck in the upgrade loop, every time I start to run, I get a warning that my disc is damaged, Disc utility can scan the disc and recommends repair, but the repair options are greyed out. Can't restore from my time machine backup as the disc can't be found, and I can't format the HD there is a warning that the 'disc can't be ejected'. Safe start mode doesn't seem to work either. Each time I restart I go straight back to the upgrade front page. It's all a bit weird, I've never had a problem updating before, everything was working fine before I upgraded, thankfully I made a time machine back up right before I downloaded mountain Lion. I can't think of what's gone wrong, unless I have been unlucky enough to have had a disc failure at the same time as doing the upgrade. Disc in question is an aftermarket Momentus XT 500GB. Is anyone able to help before I pack up my stuff and head to the Apple store on Saturday?