Ignition lock. totally locked

One week ago my 2001 Tahoe ignition lock refused to budge (I couldn't turn it from the locked position in any direction). I kept playing with it (turning the wheels, adjusting the steering wheel, banging on the ignition lock) to no avail. Eventually it just started as if nothing was ever amiss. I should have gone straigh to the dealer...
Tonight it happened again but after 45 minutes of "playing" with it...nothing (I was stranded).
Does anyone know a work around so that I can get it started and take it to the dealer?

break off the black part of the lock cylinder end where you put the key in. next look for a rectangular shaped black bar on the bottom (i believe) of the cylinder, when you put the key in it is supposed to pull this in allowing you to rotate the cylinder. insert the key and take a small screwdriver and push the rectangular bar in and then turn the cylinder, you will need a new lock cylinder and tumblers, just a thought but you might try a new key, dont have one cut from your worn out key, you can go to the dealer and they can cut you a key from your vin number. good luck