Hi, I have a late 2008 macbook (http://support.apple.com/kb/sp500). However, lately, it freezes a lot, and when it does, there are like those small pink lines running over the screen from the top of the screen all the way down... When I restart, however, everything start up normal (though it sometimes already freezes while starting up (when the apple logo comes on screen). Does this show that the video card is broken? And if it is, is it possible to replace the broken video card, or is it on the main board? It has a NVIDIA GeForce 9400M 256 MB video card.