Was using it one day and it went to a grey screen. Ended up trying a few things I got from forum searching but the only thing that solved it was a complete reinstall of OS X. Before this I did a complete backup and thought it would be a good time to completely erase my ssd and start again. Everything was ok for a few days then it started freezing and playing up again.now it won't startup and it won't boot in safe mode etc and gets a progress bar which goes about ¼ of the way and then stops like this. Any ideas or do I need to try and struggle to get a genius appointment??