Hi, I just got into the mac world with my powerbook (which i was wholeheartedly satisfied with) but lately it intermittently freezes up and gives a gray screen (like the windows blue screen of death) that says I have to restart my computer, and says it in several languages. It happens most frequently when I'm playing movies with quicktime, but it has also occurred randomly while using OfficeMac and other programs. Any ideas? If it's a virus, what's a good antivirus for mac? Thanks!