I searched the forum and see other sleep issues but none quite like this. My wife has a 2007 or 2008 Mac Pro running OS 10.5.8. Several months ago, it started having this problem: after being in sleep mode for any length of time, usually an hour or more, when pressing a key to wake it up, it restarts instead. It doesn't seem to do it when asleep for only a few minutes, but anything longer and the problem occurs. It did that for awhile and then the problem seemed to resolve itself. About a week ago it started doing it again. The applications that are usually running are Safari, Firefox, Entourage, occasionally Word or Adobe CS3. Any help would be appreciated. Thanks!