Replay Music can record any sound produced by the sound card (as a direct sound recording software). It is capable of recording from any music service or web-radio stations including Rhapsody, Napster, iTunes, Yahoo Music Unlimited!

You must be using a wrong Input source. Please check back your Input source in the Replay Music settings.

There may also be a problem with the Output source of your player. The web-site uses embedded Real Player to stream files. Check the settings of your Real Player.
I've used Real Alternative and the default output device of the Windows Media player classic. I was able to record from the embedded player with Replay Music. And I was able to right-click on the player and select "Play in the Real Player" to play and record Real Stream from Media Player Classic.