I had the same problem and went to the Microsoft Online Support, they gave me the following instructions quoted directly from their e-mail back to me:
"This issue may occur because of a corrupted SoftwareDistribution folder. We will rename this corrupt folder so that a new one is created when you access the site. Please follow the steps I have listed below.
We will first stop the Automatic Updates Service
1. Click Start. Choose Run.
2. In the Run box, type services.msc. Click OK.
3. Right-click the Automatic Updates Service. Click Stop.
After Stopping the Service we will rename the folder C:\Windows\SoftwareDistribution
1. Open Windows Explorer. Navigate to the Windows folder
2. Click on the + next to the Windows folder
3. Navigate to SoftwareDistribution folder. Right Click on the SoftwareDistribution folder
4. Select rename from the Menu
5. Rename the folder to SoftwareDistribution.old and click Enter
6. Now restart the Automatic Update Service.
Now restart the Automatic Updates service
a. Click Start. Choose Run.
b. In the Run box, type services.msc. Click OK.
c. Right-click the Automatic Updates Service. Click Start.
Now disable any firewall and antivirus software that may be running in the background and go to
http://windowsupdate.microsoft.com check whether the issue is resolved."
This cured my problem hope it helps you. Good luck!
Mark