Well, it's not often this forum fails to provide any answers within 24 hrs. However I managed to find the solution myself in the Microsoft Community site so rather than leave this one unanswered here it is.
Windows Vista and Windows 7 users follow these steps to repair the .NET Framework 4 [or .NET Framework 4.5.1] installation:
Close any currently running applications.
Click Start, and type Uninstall in the Search box and then click Uninstall a program.
Right-click Microsoft .NET Framework 4 Client Profile [or Microsoft .NET Framework 4.5.1] to launch the .NET Framework 4 Client Profile [or Microsoft .NET Framework 4.5.1] Maintenance dialog and click uninstal.
Select Repair .NET Framework 4 Client Profile [or Microsoft .NET Framework 4.5.1] to its original state and click Next.
Allow the repair to complete and then click Finish.
Click Restart Now to restart your computer.
Run a manual check for updates and attempt to install the updates again. After running the Repair, reboot then test by running a manual check for updates & seeing if the .NET 4 [or .NET 4.5.1] updates will successfully install now.