To resolve this problem try the following:
Stop Windows Update Service
1. Click Start – type “services.msc” in search box and launch services.
2. Look for the Windows Update service, right-click on it and click Stop.
Rename SoftwareDistribution folder
3. Rename the c:\windows\SoftwareDistribution folder to something like SoftwareDistribution.orig
4. Now, start the Windows Update service by right-clicking the service and select Start.
Now try to run Windows Update and it should recreate the SoftwareDistribution folder and start downloading the updates.