Im having truble making an audio CD.

I have no issues making a data Mp3 CD however I would like to make a audio mix CD that can be played on normal CD players and downloaded and installed k3b. When I open the program I can find the files that I want to be burnt. I take the Mp3 file and drag it to AudioCD0 box. But then I get an error message saying Sorry - KB3 Unable to handle the following files due to an unsupported format:
You may manually convert these audio files to wave using another application supporting the audio format and then add the wave files to the K3b project. I dont want to manually convert my files I want a program to do it for me. Is that to much to ask? Any who I am running Ubuntu 7.10 and have all the updates installed if that's important. Thanks For your Help!