I haven't had this problem, but I've heard it's common on GM's with the dash mounted key cylinder. The only fix is to replace it. To prevent it from happening again, keep your keychain light. I have my valet key on a ring by itself (and a plastic bottle opener, so it's easier to find in my pocket) and just use that for driving the car. I keep my master key with all the rest of my keys on another chain. It serves another purpose, too, by making it nearly impossible to lock my keys in my car
