I acquired my 97 Sable in May of 2006 and ever since then I have this intermittent problem of the interior lights staying on and the driver's door lock popping back up and not locking when the door is clearly shut. The problem will come and go for a couple days at a time every few months or so. The only thing I do is spray the door jam and locks with a silicone spray. Sometimes this works, other times nothing helps. There have been times when the stupid light stayed on for probably an hour or more. I have also found that when the door won't lock I can lock it with the door open and then shut it and it will stay locked, but when I have the door shut and try to lock it it won't lock. This is just a very annoying electrical problem, but since it happens so infrequently, it is impossible for a mechanic to diagnose properly.

I had the same problem with the interior light coming, and staying on. It is definitely annoying but it's really not a hard problem to fix. All you need to do is take out the screws on your door trim and carefully take off the covering. once inside you'll notice a few "motors" and what nots for your power locks and windows (if Equipped). you'll also notice that the Hinges for the door itself run into the inside of the door. All you need to do is spray a healthy amount of WD40 or your favorite De-rust or whatever onto the inner hinge and Viola. left it sit for a few minutes, half hour maybe, to get the lubrication into the hinge itself and there you have it. (I'm not promising This'll Work, but it did for me).