I have taken a look on this issue, and this is what I think :-
1. It is not a hardware issue otherwise rolling back to 10.6.8. Will no work.
2. I saw a little metal âclickâ on the top of the entrance hole of audio in/out jack, a short term solution is either to insert an earphone or an optical cable and uplug it afterward, which would drive to run the audio driver.
3. Hence, I believe there is a problem only with certain model of MBP, after upgrading to Lion the software fails to âclick onâ the audio driver of the volume control.
Before, Apple to release the new update to fix this issue, I always insert an Tousling to mini optical adapter (without cable), which helps.
http://www.amazon.com/Toslink-To-Optical-Mini-Adapter/dp/B004T67EZK