I would make certain that the OS X and the firmware are up date as a first step. Assuming they are one thing that springs to mind is reset of the System Management Controller (SMC) since power issue, see this Apple Support kb article
http://support.apple.com/kb/ht3964
Beyond that obvious thing, testing whether your issue is hardware or software-based is a good way to proceed. There is an excellent step-by-step Apple Support kb article that tells you how to proceed
http://support.apple.com/kb/TS1388
It is always possible that you are unfortunate and your computer has developed another hardware fault, in which case contacting Apple service is best way to proceed, can run Apple Hardware Test (AHT) as end-user diagnostic to get more information, but professional Apple Support has more diagnostic tools avaliable if it doesn't identify anything.
