Here are some steps I just did to get my CD Changer to work again after displaying the "No CD Changer" message:

1. With car off and all doors shut pull power connector out of back of CD Changer.
2. Turn ignition on but don't start car
3. Hold finger on eject button of disc cartridge while plugging power connector back into CD Changer. (this should eject the cartridge)
4. Insert cartridge back into CD Changer
5. Turn ignition off and take key out of ignition
6. Put key back in ignition and turn on but don't start
7. The CD Changer should be resetting (it will grab each disc one at a time until it has checked all 6 discs)
8. Push CD button on radio to play CD's

I think there is something electronically wrong with the changer. So this problem is bound to occur again, but at least I can keep it going with these steps until it completely craps out.