Last night i went to the movies with my brother and we took my car. Getting there was fine, my 98 S90 started right up no problems and has been since i got the starter rebuilt. No unusually sounds or activity from the car. We were probably in the movie theater for 2 1/2 hours came out and tried to start the car, i turned the key just enough for the electrical stuff to come on and it did. When i tried to turn it the rest of the way everything shut off. The engine didn't even try to turn over. I Thought my battery was dead but after about 10-15 secs. the cabin lights came on by themselves. I tried to start it again and again everything shut off. I waited 10-15 secs. again and the lights came on but turned on and off by themselves a couple of times like it was possessed. I tried jumping the car and it worked until i disconnected the negative line from the engine block and it just shut off leaving me to believe that it's the alternator. The only thing that's puzzling to me is that the warning light for the battery and alternator never came on.

One thing that i also thought off is that about a week ago i changed out my factory stereo for a new JVC. All the specs as far as power were the same as the factory one but the factory one had an anti theft mechanism on it and i didn't know if the car might think that someone was trying to steel the car and that's why it won't stay running?

I did disconnect the battery and reconnect and it seemed like i had more juice for a second but then everything shut off again.

Please help