Cadillac: 89 Cadi Eldorado - Anti Theft System Error., faulty chip, radio work

Question
Have an 89 Cadi Eldorado that won't start.  Here's the history.  About 2 weeks
ago the battery went bad.  Replaced it.  Over the past weekend, car wouldn't
start and upon lifting the hood, realized that the screw that connects the
battery to the car, was stripped out in the battery.  Got another new battery.  
Now, car won't start, turn over, or anything.  Lights and radio work though.  
Get a message on the Driver Information Center (digital - below the radio)
saying something like ..."Invalid Key".. "Anti-Theft System Warning." Then
asks you to take key out and re-try in 3 minutes and does a count down.  
When re-inserting the key, the same thing happens all over again.  Anyone
have any experiences with this type of problem?  Any suggestions are greatly
appreciated!

Answer
Could be faulty:

Chip in the key.
Electrical contacts in the ignition lock.
Pass-key module.
Starter enable relay.

I can provide you with some test procedures and PICTURES that you can test some parts of the system. However you may have to have the dealer use their special test integrator to check all the systems.

e-mail me at: onlineautohelp@msn.com