Little Help? Open Door or Turn on Light and Radio Goes Out

[jb3t]

So this is a wierd one with my 78 C10. I have an after market retro radio that's been working great. Tonight, I simply added an extension to the audio cord (for an iPod plugin that I snaked under carpet). When making sure the wires under the dash were not showing, the dome light went out, as did the stereo. Then, I closed the door and tried the stereo again and it came on. Then I opened the door and the under-dash light came on, the dome light did not, and the stereo went out. Then Inshut the door again and was able to turn the radio on but when I turned on the light (using the headlight control), the under dash light came on and the stereo went out (no dome light). So... When the lights are on, the stereo goes off.

I did not touch any wires when doing this, I simply tucked them up under the dash. I checked every wire and do not see anything shorting. The stereo is grounded. The stereo appears to be wired into the same wires that run the internal lights.

Any clues? This is a head scratcher. I've checked everything I touched.