As of the time of this posting, RadioTuner is not compatible with the new intel macs. Sorry.
The issue is that RealPlayer is not yet available as a universal binary (i.e., it does not run natively). Dashboard on the other hand runs natively (of course) and so the two components just don't like working together.
You probably notice that a live stream works in the standalone RealPlayer. You'd think that it should work in RadioTuner too, right? RadioTuner uses the RealPlayer Plug-in... try listen to the same live stream embedded in a webpage (you'll find plenty of them
here). If you use a browser that runs natively (e.g., Safari) the stream will not play. This is the exact same problem you encounter with RadioTuner: RealPlayer Plug-in is not universal, Safari is.
So, until RealPlayer is available as a universal binary you won't be able to use RadioTuner. But hey, you still have a cool intel mac. :)
Cheers,
Markus