I have a Macbook 2 GHz Intel Core 2 Duo with 1 GB ram and Mac OS X Version 10.4.11 and here is my problem: Whenever I leave it unattended with iTunes playing, after 20 minutes or so, iTunes and all other programs shut down and the Macbook restarts itself. The only exception to this is when there is more than one tab open on Firefox and the program can't quit because of the restriction on closing multiple tabs. In this case, all other programs quit but the computer can't restart. It seems to happen only when iTunes music is playing on the background and I'm not using the computer. When I close the lid to put it to sleep there's no problem. I don't know if this is due to iTunes, Firefox or something else, it's really frustrating. Can anyone help?