Repair the .Net framework 4.0 in the control panel:
Click Start
> Control Panel
> Programs and Features
, select Microsoft .NET Framework 4 Client Profile
, and click Uninstall/Change
.
In the Maintenance screen that opens, choose "Repair .NET Framework 4 Client Project to its original state"
and click Next. After the repair completes, click Finish. When you return to Windows Update, the .NET patches should install without a hitch.