Many (not all) Internet Radio stations on iTunes have stopped working

I am also asking this question of my ISP because the problem seems to happen no matter what I use to playback the stream. Radio.com and iTunes both cannot play most, but not all stations.

I'm using a fairly new iMac running up-to-date Yosemite and no firewall running. I am using Time Warner Cable and have an Airport Extreme router. I have checked this on an old Windows machine just for kicks and it has the same problem.

On my iPhone, running Radio.com, it does the same thing if I'm connected to wifi, but when I turn off wifi, it works fine.

That makes me think either my ISP or my Airport Extreme Router is the cause of the problem.

The streams were all working just fine and then one day last week, they just stopped playing.

It is very strange that some stations play, which makes me think there are some urls being blocked by the ISP.

Does anyone have any suggestions?

Thanks.