Funny! (And a hint for the last level)
I enjoyed this. a simple concept with just the right amout of difficulty.
As for the last level, I found the same "glitch" and since I am certain I have the last version of flash player, I think the fault is not there.
Eventually, I've been able to pass the level hitting the right portion of the head (right in the left/right meaning), while hitting the center or the left part brought a fail.
To mr Raitendo I say: Could it be that the collision check is made after a frame for some reason? Since the weel is spinning very fast, the shift would be big enough to led to the error, while in the other levels it doesn't shift so much and the collision is almost accurate.
(Just trying to help)