Im currently having a hard time of solving this problem. I had just upgraded my website to Silverlight 5 and this message is what i get:

I have take a look at the Microsoft-Silverlight Configuration dialog box and verified that application storage is enabled:

This is happening only to safari browser and windows 7 OS. Please any help will be appreciated much.
Thanks,
Apparently, Silverlight 5 doesn’t support Anything Safari inside Windows 7, but it works well on Mac. Here’s a good site for your questions.
http://www.microsoft.com/getsilverlight/locale/en-us/html/installation-win-SL5.html
Maybe tell your client that it really isn’t supported. Hope this helped.