I've heard that you can unhook the battery for 30 minutes and the Mach 460 head unit will reset itself and you can eject the cd. Won't hurt nothing to give it a try. This will also make the ECU re-learn idle and fuel trim. After you reconnect the battery and try to get your cd out do the following to complete the idle re-learn.
Start the car and let it get to normal temperature.
Let it idle for at least one minute
Switch on the A/C to Max and Idle for at least a minute
Turn off the A/C and go drive normally for at least 10 miles
I hope that gets your cd free!