I have a Mac OS X laptop and its been fine all year until now. Yesterday, it started freezing. (The only application I had open at the time was Safari. I have never installed anything on it, either.) I could move the little arrow around but when I tried to click things it wouldn't work, then I would restart and it'd do it again. Now today, i'll use it for about 15 minutes then it'll say "You need to restart your computer. Hold down the power button." Then I will do so, and it'll just do it all over again. Whats doing on? How do I fix this? Thanks in advance.