I recently restored my system from Time Machine and now when I press spacebar to do a quick preview on files it shows me nothing. Doesn't matter what type of file it is, it fails. Any idea what I can do to fix this?
After doing a bit of research on the matter, You should read this article:
It recommends to reinstall Mac OS X v10.6.2 Update (Combo)
Also take some time to read this from Apple Support: blank quicklook