BleepingComputer.com: Sound not working

Just now I installed the MAC OS X update and the iTunes update but after getting to about 95% saying "Moving files into place...", it froze, and after spending 15 minutes without moving a pixel, I power cycled it. Now, the sound doesn't work; the volume symbol is grayed out and pressing the volume changing keys gives a grayed out symbol and a circle with a slash through on the bottom. What do you recommend doing?
OS: Lion
Hardware: 2008-2009 13 inch Macbook Pro with double RAM"
Edit: Upon further inspection, the Sound preferences says "No output devices found" and "No input devices found". Opening GarageBand gives "Selected driver not found. (-10202)" but it still loads. Opening iTunes and playing something causes no increase in the progress bar of the song. Opening a song or movie with Quicktime Player causes the window to freeze and refuse to move around, but doesn't freeze the app, and opening something via Open Recent gives "This operation cannot be completed."

This post has been edited by Saposhiente: 04 February 2012 - 12:31 AM

Things I would try.
Boot into Safe Mode. Reboot normally.
Download and install the latest Lion COMBO update.
Download and install the latest iTunes.
Repair Permissions with Disk Utility after each install.

*wakes up*
(Downloading the lastest Lion COMBO and the latest iTunes and nothing else was what broke it)
Because it was late, I just backed up with Time Machine and then reinstalled, and now it works. Thanks for the help anyway! I didn't know about Safe Mode before.

Ensure the below step,
Going to the Sound Preference Pane and making sure that nothing is muted and also check the output is directed to the internal speakers and not to some external set.