I just wanted to point out that the newer versions of CCleaner have Microsoft Silverlight checked for cleaning. What happens is every time CCleaner cleans Silverlight data, when you log into Netflix your PC will be reactivated even if it was already activated. This causes all your device slots to fill up.
If you simply uncheck MS Silverlight for cleaning the problem does not occur. Took me a little while to figure out why this was happening. Netflix customer support was unaware of this issue.