I've seen this before. It could be one of different issues. Seeing that AvoK95's solution didn't work, try one of these:
1. Go to where you change your account picture, PC settings, general. Keep that open and refresh your Windows a few times. Try the update now. If it works, then you had one of the famous Windows 8 bugs.
2. If that didn't work, go to CMD as admin, type:
net stop bits (hit enter)
net stop wuauserv (hit enter)
Then download this file:
http://download.microsoft.com/download/F/2/2/F22D5FDB-59CD-4275-8C95-1BE17BF70B21/WindowsUpdateDiagnostic.diagcab
and run it. This should reset your Windows Update Component. If both didn't work, let me know, so I'd suggest more solutions.