Have you tried resetting SMC?
http://support.apple.com/kb/HT1411
The System Management Controller is an integrated circuit (computer chip) that is on the logic board of the computer. As the name implies, it is responsible for power management of the computer. It controls backlighting, hard disk spin down, sleep and wake, some charging aspects, trackpad control, and some input/output as it relates to the computer sleeping.
Over time, the settings in the System Management Controller may become unusable, which can result in operational anomalies with the computer. Examples include not turning on, not waking from sleep, not charging the battery, or not recognizing the AC Adapter, among others.
and/or the the PRAM?
http://support.apple.com/kb/HT1379
http://support.apple.com/kb/HT1242