I was able to add it without any problem.
Have you perhaps run out of favorites? There is not an infinite number, but I don't know what the total number is. I suppose you could prove this by removing one other one and then try adding ShoHD again.
Add another channel after SHOHD after it on the list, then it will keep ShoHD and drop the one below it you added (or thats how I think it worked on mine)