I've got a different problem. It's working for me on my iMac but one of the "stations" played about 9 or 10 songs and then stopped playing. Now it won't play any more songs. I shut down iTunes, reopen, click it's play button and it will show me the Nissan ad (is anyone else doing video ads on iRadio?) but no music. It's like it ran out of songs to play after just 10.
The "station" is "'60s British Invasion" in discovery mode. About 70% of the songs it played in that 10 were songs I already owned (I would think "discovery" would be playing similar songs NOT already in my local library). And, of course, it offered to sell me all 10 songs even though I already own 7 of them.
All of the other "My stations" will play just fine but I haven't tried to play 10 songs in a row with them yet. Is there some quota on how many songs someone can play on any "My Station"?