Door Ajar 2002 Ford Explorer

I bought a 2002 Ford Explorer in June of this year (2005). When I first got it every once in a while the door ajar would come I would get out and open and close every door and everything would go back to normal. So then on November 11, 2005, the door ajar light came on and has not gone off since. So this causes my interior light to stay on for a few minutes when I start driving. So I called my buddy who is an assembly line worker for Ford and told him of my problem and he suggested that I just disconnect and re-connect the positive wire on the battery so I did that and it solved the problem for about an hour. Then the problem got worse. Now the door ajar light is still as is the interior but now the lock button does not work on the driver’s side door neither does the buttom that adjusts the side view mirrors, the car does not lock when i put it into gear and start to drive and and when i turn off the viechle the radio automatically turns off instead when I open the door like it is supposed to. I know some of these problems are not major I just want to know what is wrong with my truck, any help would be appreciated.