I know I've had trouble with the Flash players CBS and Clear Channel use on my Linux box. Since Linux is similar to a Mac, you may be experiencing a similar issue. I can usually stream a few songs on AOL Radio or Yahoo! Launchcast only to have the stream suddenly die. The player usually just goes completely blank, but the Window is still up. I've actually not encountered a problem with the live CBS radio stations on the same player, and the Yahoo! player seems to work better than the AOL player despite them being essentially the same. I can't isolate the problem, and the best information I can find is that the Flash player install just isn't the same on a Linux box as it is on a PC. In other words, as far as I can tell, it's probably just a compatibility issue that's not likely to go away.
When it comes to Cumulus, the reason you're having trouble may have to do with them using Silverlight. Last I heard (and, in the interest of full disclosure, it has been awhile), there was no version of Silverlight that would work on a Mac. You can, however, get a basic player that will work around this. With a little digging around Cumulus sites, you should be able to find it. On my newer Linux box, Silverlight (or Moonlight as it's called in the Linux world) worked just fine until I updated the Kernel a few months ago. Ironically, my old Linux box had the opposite problem. I had what I have now until I installed the Real Player, which had the additional codecs, through Helix, that I needed to play Silverlight streams. That, unfortunately, didn't help on my newer Linux box. So, I usually just stream those stations through the command line. I figure I can type, or copy/paste, the link directly since you have to be a dweeb to be using Linux anyway!
Something you might be able to do, at least with terrestrial stations, is to check out TheStreamCentre.com. It has a good list, that's usually updated quickly, of streaming links.
