Many if not most of us need to view Real Audio files on the web. RTÉ, the main Irish tv station, uses it extensively, for example.
I had installed the open source Helix Player from Add/Remove Applications - or maybe it was already installed, I’m not sure. But that didn’t work for the RTÉ media. I hadn’t in truth noticed that Real Networks open source Media Player 10 was also in Add/Remove Applications, so I downloaded it from the Real Site. But that didn’t work either. Finally I noticed it in Add/Remove, but it wouldn’t install.
The trick was to uninstall the downloaded version, uninstall Helix from Add/Remove, and then install Real Media Player 10 in Add/Remove.

To remove the original downloaded player, open your Terminal (Applications/Accessories/Terminal) and type or paste

sudo aptitude remove realplayer

The relevant Ubuntu Forum page is headed Remove Skype, so it should work for most programs you want to remove.

I hope that works for you if you had the same problem.