This may be a total shot in the dark but your description sounds remarably like how my problems started. I had almost the same exact symptoms. I have traced the problem down to a bad ignition switch and a short in the radio system. I first found that my ignition switch was keeping circuits hot, when the key was removed, that should have had no current. After fixing that I checked each of those circuits and found high draw on the radio circuit. I pulled the radio and voila, no more problem. Unfortunately It looks like I did not catch it early enough as it looks like it took out several other items too. Oh, the morning I had finally narrowed down the problem to the ignition switch I walked out in the garage to be greeted by the antenna going up and down randomly. Gee wonder why my battery was dead, huh!