Same thing happened to me once

I have no idea what went wrong. Had enough space. I was able to get almost the complete file back using Restoration (approx 6 minutes of the movie missing)

http://www.gnutellaforums.com/showth...threadid=47967

Use your computer as little as possible until the recovery. You may overwrite parts of it by accident

BTW the file I lost was only 730 MB, so it wasn't any filesize limit causing this