problems with aftermarket stereo and factory amps?

[B.J.]

ok, here is the problem. i put an aftermaket stereo in my sho using one of the easy hookup conectors so that i didnt have to cut any wires, my new stereo sounded great, no problems at all. now i have put my factory stereo back in plugged everything back up except for the cable running from main unit to cd player, as far as i knew this was only to get sound from the cd player. now i cant get any sound from my stock stereo unless i turn it all the way up and then it just makes almost a whisper of sound. this has puzzled me greatly, i dont have the aftermarket stereo anymore to test to see if it still works. the only probs i have figured out are the fuse for the stereo was blown but once replaced it hasnt blown again. the car hasnt been driven for 6 months so i really dont know what could have blown both the stereo that was in a box and both amps all at the same time. any help would be great. thanks - b.j. headbang