Why do I have to delete and reload Silverlight constantly on Windows 7

I subscribe to Netflix and watch a lot of streaming video movies. Lately it periodically tells me I must have Silverlight to display the movies. Since I already have it I don’t know why.

There’s a direct link to the download, but even though the link works, it doesn’t solve the issue. Netflix is aware of the issue but has no solution.

I have to uninstall Silverlight and reinstall it to use it again. Netflix says other callers with this issue can’t even get it to work again at all.

The oddest part is if I use XP it doesn’t have this problem, only on Windows 7.