my imac has no sound after Lion, the system does not recognize the internal spekers.

Same problem for my MBP 17 (2011). Only solution for me is to turn Bluetooth off/on before shutdown/boot. All other workarounds described in various threads don't work for me. Come on, Apple, fix it as soon as possible!

Restart. Hold cmd R and repair permission. It's work for me.

Tried all the above and it didn't work.

Went to System Preferences and clicked the "sound" icon.

3 tabs in sound are "sound effects", "output" and "input."

Clicked output and it was on a "soundflower" setting.

Clicked on the "internal speakers" and VIOLA, sound was back.

Moraly they should not, but they likely will.

I paid £35 for Applecare on the phone and remotely to fix it - still got the problem....

I have been trying tosolve this problem for days. Your solution worked!!! Thanks

revert back to xsonw cause lion will give u alot of trouble advice i install it n it giving me problem after proble lolz xsonw is good enough for macbook