audio drivers corrucpted/ missing?

I have a Macbook. currently running 10.6.1. Just a few days ago, I went to open up iTunes and it gave me this error message:
"The iTunes application could not be opened. an unknown error occurred (-200)"

I've tried "researching" the best i could and come to the conclusion that its an audio driver because my computer wont play any sound either. when i go to youtube, no sound. Skype, no sound. even to preview .mp3's from the desktop, NOTHING!

BUT I can still open up Project files from a beat making program i use, and i have audio again, but only for that program.

i've run many updates, and done all that i know... if anybody could help that would be great.
thanks for your time.

First thing to do is update to 10.6.5 using the combo update - link.

Second, run Software Update for all the other system updates you may be missing.

(And crossposting in multiple places is not an acceptable practice on any well run forum.)