I just used Pandora for the first time (since the ICS update) the other day. It worked just fine for me over 3G. But then, ICS has been pretty solid for me overall, whereas, it has not been so smooth for others.
I have the same problem and the funny part is my wife and I both the same phone and when I play pandora on my phone it loops but it works fine on her phone. I have uninstalled the app and re-installed it and it will play one song and the go into the loop...