Jammed Giant brand U-Lock. Unable to insert key The other day I locked my bike to a fence and upon my return about an hour later, I found the lock jammed. I am unable to insert my key fully into the keyhole. My friend suspects that while locking the bike, I might have removed the key too hastily, resulting in the lock pins being misaligned. 

The lock is a Giant brand U-lock. The key goes in about half way and is unable to turn. I tried forcing the key to turn which resulted in me snapping the key (luckily, I have a spare). Any help in the matter is much appreciated.
I've had this same issue happen with my Masterlock, and generally remedy it with lots and lots of wiggling. It mostly happens to me in the winter when a bit of moisture gets in there, so I don't know if it's the same issue or not.

My method was to stick the key in as far as it would go, and then repeatedly try and wiggle it back to the most locked position, while moving the key back and for laterally (or whatever the perpendicular direction would be to whichever way it turns.) Just go back and forth a lot - sometimes it works quickly, but sometimes it takes ~15 minutes. Either way, that's always eventually worked for me.