Did you install the latest supplementary update? That might be the problem. Some of us have been experiencing problems after installing it. The fix, for now, is to reinstall OS X, reset SMC and ignore this supplementary update.
Resetting the SMC
Threats of violence. We take these seriously and will alert the proper authorities.
Posts containing personal information about other players. This includes physical addresses, e-mail addresses, phone numbers, and inappropriate photos and/or videos.
Harassing or discriminatory language. This will not be tolerated.