iTunes Radio just stops playing, or sometimes doesn't even start

I've got a few stations that I have created in my iTunes Radio, that just won't open and play even though they used to, and some times they will open and start to play for up to 10 seconds then shut. I've created new stations, and eventually (w/i 1/2hr of playing) they did the same thing.

Does anyone know what the problem is or how it can be fixed?