I've seen the color (the burning side) of the CDr's mess with cd players, not reading them right and such, but never switch to radio. That's kind of a strange one. If you are using a colored disc, you may want to try a different brand to see if it still does it. What happens is the laser starts out red, bounces off a blue-backed cd (or whatever) and the receiving eye gets hit with a purple bit of information instead of red, its not really sure what to do with a purple light.
If no one else pipes in with an answer, I'd take it to the dealer and ask them.
Hope that helps...
-There are 10 kinds of people. Those who understand binary, and those who do not.
-If we ever forget that we are One Nation Under God, then we will be a nation gone under...Ronald Reagan