I have got the same problem. It has started around 02/23/2011.
Samsung support could not help.
I have a LN40C650 that about two days ago stopped allowing me access to the Samsung Apps to download new Apps. Programs that were already downloaded and installed work just fine. When I click the Samsung Apps menu button in Internet@TV, I receive the message "Network Interference Occurred. Try Again Later."
Just this evening, none of my Apps work. Even the downloaded ones that worked just a short time ago are also experiencing "Network Interference".
I have changed nothing in my network settings nor experiencing any problems with any other devices in my home on my wireless connection. This issue seems to have conicided with a software update (I was recently prompted to update to 2011/01/31_001035), but I am not sure. It does seem to be a more widespread issue though as others on CNET have come across this problem in recent days: http://forums.cnet.com/7723-6035_102-518504-0.html?tag=rb_content;forums06
Is this a more generalized widespread problem that users should wait out? Or is there a solution I can look into? Can anyone please help? I have received different answers from Chat Support (which suggested a reset, which has done nothing for others with the same problem), to Phone Reps who said the server was down for varying amounts of time and were not entirely helpful.
Please help as I purchased the LN40C650 over other TVs for the App features, and also have UN55C8000 waiting in the box that I am now very concerned with have the same problem if I choose to set it up.