can't index files

Hello, my search doesn't work any more. When I click "All my files" in finder, it's empty. I've tried to add my hard drive to the Privacy window as others have advised, but I get a Privacy Error when attempting to add the hard drive, "The item couldn't be added or removed because of an unknown error."

The search also does not work in imail as well.

Running

OS X 10.8.2 (12C60)

Server OS

Any thoughts anyone?