Have you ever encountered errors with Windows Update or had it just stop prompting you all-together? This might be the solution to your problem. Either way it is a web page at Microsoft that will provide the right tool depending on what Operating system you are running.
To run the utility navigate to http://support.microsoft.com/kb/971058 and click on the Microsoft Fix It icon or link:
You will have one option that can be selected, only use this option if the first attempt without it checked was not successful:
After running the utility in either mode an additional screen will pop up with other options:
If after a restart you still experience issues, you can run the utility again to access the help links in the utility. Microsoft does provide free support for windows update issues.