I'd originally registered having had the same problem, but in the time it took to get approved I found a solution.
This feels like a bug in the software, having Googled the problem you realise there are a few people out there who have experienced the fault. Something for Samsung to look into and rectify perhaps?
You can fix it by resetting the TV completely via the engineer's menu. To do this:
Put the TV in standby mode
Press INFO, MENU, MUTE and then POWER on the remote.
You should now be in the engineer's menu. I would recommend being careful cos I suspect there's some scary stuff in here. Use UP and DOWN on the remote to move through the menu. Using left or right will select the option so... don't use left or right
In the right hand column there is an option titled RESET, highlight this option then press OK to select it.
You now, essentially, have a fresh-out-the-box TV. Switching it on will take you to the initial Plug-and-Play menu. All you original settings will be lost, but at least now you have more than one channel to watch.