96 GP key? not working

Hi, I'm new here but still have a question that I hopefully will get answered..
My 96 GP won't start. The lights radio EVERYTHING works but won't even crank. I KNOW it's NOT the battery as it's new. I've replaced the starter selinoid ( sp ). So that's new too.
One time it starts fine the next second the dang thing won't even crank:banghead:. Not even a sound.
I've tried the alcohol on the key and chip on it. It WORKED for awhile. Now even my wifes key doesn't work all the time.
The stealer wants $150.00 just to look at it!!!! And they said it might be in the $600.00 + range to fix it.
ANY help would be great. I thank you in advance, Pat
1996 3.1 GP SE with 137,000 miles.

Since cleaning the key worked for a while, I'd say the issue is the passlock sensor in the ignition cylinder. You could try starting it neutral, and if that works, it could be a neutral safety switch issue.

Could be the key or switch . That key has a black chip on the blade which is really a resistor. It is an anti theft device , the chip makes contact with some leads inside the ignition , if the value of the resistor is wrong the car won't start . Could be that your key is worn or switch is worn . Have a new key made and see how that works , if it doesn't help you may need to replace the ignition switch. If you have a locksmith in your area , I am sure you can get a key or a switch for half the price of the dealer. Kevin / N.S.

You can also try a key re-learn. Put the key in the ignition, turn it to on (w/o starting the car) and leave it for 10 min. Then turn the key off for 10 seconds, then attempt to start car.

If your keyring is heavy, it can also cause the resistor to not make contact. Had that happen in my '94 SE a couple times, so I lightened the load on my keyring, and it stopped.

Well, it SEEMS to be working again.. I'm using the wifes key ( not used much by her and not carried in her pocket with a million other things )
I've cleaned it and tried to clean the inside of the ignition ( alcohol on key )
So my fingers are crossed ..
THANKS to each and everyone of you !!!
Pat