You don't need a locksmith. You simply need to understand the new flat key mechanism used by BOTH OnGuard and Kryptonite on their 2005 model U-locks. The keyway where you insert the key has rotating plates. If someone tries to pick the lock, the plates rotate and make picking more difficult.
However, if you are inserting the key, and begin to turn the key before the key has passed the bottom plate, the plates rotate, and the lock refuses to open. You can also turn the plates by turning the key slightly as you withdraw the key from the keyway.
Both OnGuard and Kryptonite place a red warning sticker on their 2005 locks, warning owners to insert the key fully before beginning to turn the key. However, until you "play around" with the lock a bit, you won't understand how to prevent accidently plate rotation, or how to cure it.
If all of the plates are aligned correctly, when you look into the keyway you will see a rectangular open box with smooth sides that extends to the bottom of the crossbar. If a plate has rotated out of place, you will see a jagged edge along one side of the keyway.
The solution sounds complicated, but takes just five or ten seconds after you have practiced. You take the tip of the key and gently rotate the top plate so it is perfectly aligned with the second plate. Then you stick the key a bit deeper, and rotate the second plate so that it is perfectly aligned with the third plate. Then do the fourth plate, and the fifth plate. When all of the plates are aligned, the key turns very easily. If the key resists turning, or you must use force to turn the key: STOP...the key is NOT at the bottom of the keyway, and you will break the key.
When I got my first "flat key" locks, I accidently jammed them a couple of times. After I discover HOW I was jamming them, and realigned the plates, I've never had the slightest problem. Just work the key ALL the way to the bottom and turn the key lightly and the lock pops open.