I'm with remmons on this one. I know, scary, but hey, whatever.
When you turn your key to the OFF position, it pulls up a rack (in many older GM columns). The rack pulls the rod up. The rod disconnects the circuit. At the same time, there is a pin on the side of the cylinder that engages the white connector with the two brass tangs. That is your "key in ignition" buzzer warning system. It also extends that round pin at the very top of the steering column. This pin fits into one of the slots on the lock plate preventing the steering wheel from turning when the key is out of the ignition. This lock pin is also what creates what is commonly referred to as "steering wheel wrap up". If the steering wheel is turned with the key removed, the pin can bind on one of the notches and not allow the key to freely turn. Pulling the wheel to one side or the other removes the bind and allows the key to turn.
Now are you starting to see why having the proper cylinder installed in the column, and seeing what your actual column looks like, is very important to help diagnose a potential cylinder or switch issue? Lots of things come together in a very small area and all play off each other.