From what research I have done over the past 24 hours, it is true that there have been ongoing problems with WMC and Netflix. However, I believe that there is now something new going on.
I Have tried every combination of fresh install, registry hacks, dns change ups, etc, to no avail. On all of my systems, with multiple netflix accounts and from multiple ip addresses.
The only thing that I was able to find, when running Fiddler (web debugging tool), there is a 404 error when a movie is selected in WMC, before it is even played. Also, I was able to remove computer devices from my netflix accounts, now they do not show up despite being able to log in via WMC and play through any browser.
If I had to guess, netflix made some sort of change (they have been doing a lot of that lately).
If anyone is still able to stream Netflix via WMC (windows 7 x64, home, pro, or ultimate) I would like to hear about it, as there could be something I am missing.
For now, I am just going to wait and hope that the problem is fixed or a hotfix is rolled out.