Today, I brought back up an old machine of mine running windows 7. It had been a good 6 months since I've last used it, so naturally, windows updates was not working.
I managed to find a nice thread on social.technet: http://social.technet.microsoft.com/Forums/en/w7itprogeneral/thread/6a8889a8-65b2-4012-9cf8-2689f47b21e4
stop Windows Update Service
start Windows Update Service
check for updates
Hope this helps if you run into the same issue.