I'm also having the same problem - just started a couple of weeks ago. Prior to this, it was also working fine for almost 2 years. No changes to the Blu-Ray set-up, so it has to be something at Netflix.
Also, once I go to the Netflix website, enter the activation code from the TV screen, Netflix streaming starts up after a few seconds and works fine, but the Netflix website gives me an error that the code is no longer valid and to enter a new code. Just for kicks, I tried getting a fresh code and reactivating it, but I get the same error message from the Netflix website.
I reset my router and also powered-down the Blu-Ray by unplugging it for several minutes, but nothing has fixed the problem. I also tried deactivating the Blu-Ray player on the NetFlix website, then reactivating - no change.
I called Netflix and they, of course, blamed it on Samsung (I saw that one coming) despite the fact that nothing has changed on the Blu-Ray, and it works fine once I reactivate (every day!).
I should note, though, that this problem started at roughly the same time that we changed our service plan from 3-DVDs-at-a-time to 1-DVD-at-a-time. And, of course, Netflix said this didn't have anything to do with it. But it seems like the Netflix database is daily telling the website that the Blu-Ray player associated with our former 3-at-a-time plan is no longer valid, so the reactivation is not "sticking" to our current 1-at-a-time plan. I understand this shouldn't matter since it's the same account, but who knows how their database software works.
My Samsung P2500 BluRay has worked fine for 2 years. Now, it won't hold the Netflix activation code. I'll activate it and it works fine for that day. The next day, it's not connected so I again need to activate it. This has been going on no for several weeks. I've updated the firmware, still the same problem. No help from Netflix or Samsung tech's. It must be a Samsung issue though, since I also have a Wii connected and it stays activated with no issues (don't want to use it though as the picture quality is not as good as the BluRay player).
Any ideas on how to fix this?