I have a problem with a 15" MacBook Pro (2011, OSX 10.7.5): After being repaired due to a water damage recently, the sound was just working fine. Some days later the audio device in the status bar turned gray and the MacBook didn't play any audio anymore.
After having tried several approaches to solve the problem (e.g. https://discussions.apple.com/thread/1736638?start=345&tstart=0)
So I repaired HDD permissions and deleted
~Library/Preferences/com.apple.BezelServices.plist in normal and safe-mode of OSX. After a restart the speaker icon is highlighted again and sound was available again.
But another restart later it didn't work again. Now the approach mentioned before also didn't solve it anymore. As the soundcard was working fine temporarly I'm guessing it's just a software issue.
How can I come closer to a solution?