Level 12 and Level 23 both had me stumped until I figured out how to really use the jump ability. For level 12 use the catapult to get up to the ledge where you can jump onto the ladders, then jump across the ladders until you get to the one closest to the ledge with with the security machine. When you jump from that last ladder be sure and hold down the jump key instead of just pressing and releasing, this will give you extra "hang time" and just as you hit the ledge press jump again while you press up on the stick. This will cause Clyde to twirl and grab onto the ledge. It took some practise, but once I figured it out I was able to do it pretty consistently.
JethroXPProgram Manager, Xbox Live
Post provided as-is with no warranties and confers no rights