Hi tyler27. The most likely cause is bad solder connections in the radio. If I'm right, you will not be able to change the radio stations when the problem occurs.
If you ARE able to change stations, two possibilities come to mind. Since the clock stays on, you know the switched power from the ignition switch is working properly, but there could be a problem in that circuit after the radio. I would try to find the remote amp and use a digital voltmeter to monitor the voltage on the power wire when the problem occurs. From your description, it sounds like there's a relay in the circuit that is turning off. The relay would be turned on by the radio when 1) the ignition switch is on, and 2) the radio is turned on. A bad solder connection in the radio would remove the turn-on voltage for the amp relay.
In some radios, the voltage on the separate memory circuit must be present for the radio and / or remote amp to turn on. I suspect this circuit isn't the problem because at some point you should have noticed the radio's clock go back to 10:00 and the station presets would have been lost.
If you do find the voltage disappearing on the power wire to the amp, the next step would be to locate the relay you're hearing and monitor the voltages on the coil. If the 12 volts goes to 0 volts or the ground wire goes to 12 volts when the problem acts up, the relay is being told (incorrectly) to turn off. You'll need to check the service manual to see if it's the ground or 12 volt wire that's switched. If the ground wire is going to 12 volts, suspect a corroded or loose ground connection. More commonly it will be the 12 volt side that's going away. That would be typical of a bad connection inside the radio.
A word of warning about these radios. GM refuses to sell radio service manuals for their products newer than '93 models so I don't work on very many. Those that have been shipped to me have a near 100 percent failure rate of the cd laser assemblies. They don't seem to fail that often for customers, so I have to conclude the rough handling during shipping is partly responsible. I would recommend pulling the radio out and connecting a temporary wire to the "switched power out" wire, and monitoring it with a voltmeter to be absolutely sure the problem is in the radio. If you do have to ship it out for service, but sure it's packed in a lot of loose fill so it's affected less by vibration.
Sunday, February 21st, 2010 AT 1:20 AM