Steps to manually clean up a broken Silver light installation in Windows 8:
1) Download Fix it 20104 msi from here:http://go.microsoft.com/?linkid=9831161
2) Close all your Browsers and Communicator/Lync windows. If they are running, you will get following message to close them.
3) Agree to the terms and conditions and click Next.
4) Fix it will create a restore point should it needs to rollback itself.
5) Silver light removal is automatic. Once done, just Close the final window
The above steps ensure complete removal of Silver light. Now just browse to any Silver light App and a fresh new run time will be installed for you automatically.