A few people had this same problem and bought the GM steering wheel lock bypass. I also think there was a dealer fix for this removing the bar in the the steering column.
From a 2007 post:
What is the symptom of failure?
A Your steering wheel will not unlock and the DIC will display an error message "Service Steering Column Lock". Your owner's manual will instruct you to have your vehicle towed to the nearest GM dealer for repair.
Q What exactly causes this failure?
A When you insert your key into the ignition and turn it to the ON position, the BCM (Body Control Module) sends a command to your Column Lock Motor to "unlock" and then checks a status line to ensure that the steering column is unlocked. If it gets the wrong status, it will display an error message as mentioned above. It can be caused by ECL (Electronic Column Lock) mechanism failure and occasionally by low battery voltage, which sometimes confuses the BCM.
Q Can anything be done to unlock the steering column once it has locked up?
A Sometimes; turn the ignition OFF and REMOVE the key. Shock your lock motor actuator assembly by jerking the steering wheel against the stops. Re-insert your key and try again. Also, if your battery voltage is low, charge your battery or replace it.
Q If my battery is discharged and I jump it to get the engine started, the alternator is now charging shouldn't the column unlock?
A NO; The whole unlock sequence occurs before you ever turn your key to start your engine. If the battery is too low, you will probably have trouble with your column lock. Several folks have replaced their battery and the column lock problem has never occurred since.
Q What years are affected?
A All
Q Is there any solution for this problem?
A Yes, install a Column Lock Bypass (CLB) Once it fails, you may not be able to fix it without GM repair. This bypass will also work when your vehicle is parked with the key off or out.
Some people used this
http://www.ebay.com/itm/LMC5-MODULE-with-UNLOCKER-97-04-C5-CORVETTE-STEERING-COLUMN-LOCK-BYPASS-REPAIR-/230819881438?pt=Motors_Car_Truck_Parts_Accessories &fits=Model%3ACorvette&hash=item35bdefe1de&vxp=mtr