About a month ago my Macbook (which I bought 4 in May) started getting really slow when I played movies with quicktime or used Front Row. The entire computer slows down and the fan ramps up for about 2-3 minutes until the movie starts playing. After that everything is normal again until I start playing a movie or go back to the Front Row menus. This seemed to start when they updated the latest version of QT but that may be a coincidence. Any ideas what could be causing this? thx.