hi there--
could be different things. the first thing i would try would be to go to /library/preferences/systemconfiguration and pull two plists inside that folder. these are the powermanagement.plist and the autowake plist. also, i would check to see if this was connected to a peripheral device by unplugging all of them, although a device is more likely to cause a problem where the computer can't go to sleep. if pulling the files doesn't do anything i would boot to the install disk and do disk repair.
http://docs.info.apple.com/article.html?artnum=106214. and if it still doesn't make a difference, i would try a pmu reset. i believe it is called a cuda button on this model, but i cannot find specific directions. i can find them for the pci graphics, which is probably similar. if you look in your user guide there might be instructions on doing that. hope something here works for you. [ 8 ) ]
