Hi Michael,
We would like to know the following information from you for further assistance.
Do you use any active registry cleaner on your computer?
Usually, this type of error messages comes up when vital registry information has been removed accidentally. Registry cleaning programs are known to do such accidental damages sometimes.
I would suggest you to use the steps given in the link below and then check if it helps.
How to clean a corrupted Silverlight installation and then reinstall Silverlight
http://support.microsoft.com/kb/2608523/en-us
Write to us with the status of the issue. We will be happy to assist you.