Okay I was in the same boat as those who had this problem (on mavericks), but had no PlayReady folder, and thus the typical solutions above didnt work (including deleting the plugin and reinstalling).
Here is my solution that finally worked. First close all browsers then delete the following ->
/Library/Application Support/Microsoft/PlayReady [if its there, in my case it wasnt]
/Library/Application Support/Microsoft/Silverlight
/Library/Internet Plug-Ins/Silverlight.plugin
/Library/Preferences/com.microsoft.PlayReady.plist [this is actually a folder with hidden contents, delete it completely]
The rest will be in your home directory (Users/Username), as designated by "~".
~/Library/Saved Application State/com.microsoft.silverlight.savedState
~/Library/Application Support/Microsoft/Silverlight
Also look in ~/Library/Preferences and delete any files with com.microsoft.silverlight in the filename (cant remember the exact filenames, but it should obviously be related to silverlight when you see it).
Once that is done, install the latest version of silverlight from the dmg downloadable from microsofts site. Start your webbrowser and try netflix. Let me know how it goes.
SIDENOTE: I also deleted ~/Library/Saved Application State/Safari/Localstorage/http_social.microsoft.com_0.localstorage in the process, which I doubt was relevant, but just incase I'll add that here.