I downloaded Mountain Lion this past weekend & since then my computer can't do anything but freeze and run one application at a time. I have a 15" mid 2012 mbp The guy at the apple store deleted some random programs that started on boot-up that were in the background and did a hardware check... Everything checked out fine. I came back from thinking he may have fixed things but I still have the same issues. I scheduled another Genius Bar appointment tomorrow because at this point all I can think of is getting them to wipe my mac and install Lion and tart from scratch. Have you guys run into any similar situations, any tips?