I believe its an auth error. If you tried signing in and out of the app store and downloading a free app (typical fixes) and it persists, try downloading the updates manually. If youre trying to get the Mountain Lion updates the link for 10.8.1 is here http://support.apple.com/kb/DL1571 and if you already have 10.8.1 and youre trying to update to 10.8.2 the link is here http://support.apple.com/kb/DL1580 a supplemental update came for the 10.8.2 which can be found here http://support.apple.com/kb/DL1600
Like I said before, the error isnt that your software or hard drive is corrupt, it has to do with your AppleID authenticating the download, especially because OS updates are part of the Mac App Store. If you know your way around your system libraries or root libraries you can possibly fix it by deleting specific files that may be corrupted, otherwise you're going to want to back up your data and reinstall the OS.
Good luck!