It looks like the the bad Netflix karma has struck again as we're hearing reports that some gamers cannot get the New Xbox Experience enabled Netflix to work. According to reports, the Netflix activation code the 360 spits out isn't being accepted on Netflix.com, making the entire "watch your Netflix movies on your Xbox" thing a non-reality.
We have yet to hear from Microsoft or Netflix regarding the issue that some are experiencing, so you'll just have to sit tight. In the meantime, try restarting your console after installing the Netflix add-on. Some are claiming Netflix activation success after a simple restart.
[Via Joystiq, Thanks Scooter]