Ignition problem. Please help!!!

I have a 97 Blazer. When I try to turn it off the ignition will not unlock for me to get the key out. I work for a Chevy dealer and they just changed the ignition cylinder today. But after a few short runs, it happened again. Does anyone know what else the problem could be? I've read up on similar problems but there seems to be a lot of different reasons as to why this could be happening. I would appreciate any info anyone can give me.

:banghead:

The key will not come out on my 91 S10 Blazer either. I went to the dealer and purchased the electronic ignition switch module for $22. I removed the bottom dash panels and dropped the stering column. The module is located on top of the steering column about a foot down from the steering wheel.
I replaced the inginition module with the new one and I also replaced the High Beam Switch which is located right next to the ignition module.
Put everything back together and the key will still not come out so it is not the ignition module. It must be the actual lock mechanism inside of the steering column. My high beam lights now work though. The whole job took me 2 hours to do.
I took the car to a professional mechanic and I am going to pay them to fix it.