door lock problems

Hi,

i have a 1997 nissan altima, and i am having some trouble with the door locks
i just recently bought the car, and so far its been a blast except for a few things.

well this is #1 and the only big one atm.

basically the door locks do not lock correctly,
sometimes they will lock but most of the time they force to unlock and when it does it unlocks all 4 door locks,
if i lock all manually when i go to close the door it will unlock all 4 when the door is closed
although i have found a way around it i dont know why it is but when i start the engine and shut it off i can manually lock all 4 and than close it they stay locked, i was wondering what the problem is im thinking either the computer or fuse?

i have come to the conclusion if this keeps up im going to end up taking off the door closed indicater switch i was wondering if i even need this besides the dome light.

thanks a bunch.