[dnanian]

I don't have a lot of information to work with here, Lewis. Certainly, the implication is either that there's not enough space for real (unlikely), or that the file listed here (PC X in your document folder) is either damaged or being written to at the time of the backup.

If it might be damaged, try duplicating it in the Finder, then deleting the original, emptying your trash and renaming the duplicate back to the original, then try again. If it's being written to, stop the program that's doing that for the duration of the backup.

Hope that helps!