Ladder Area?!

[Neo]

You do know that clicking the mouse buttons whilst climbing results in the player falling down, right? Could that be the problem?

No, this isn't the problem... And if I try to climb up the player stops at some point and is falling down, too.

@Amn: I tried that out, too, but nothing happend.

If I click on the ladder area I get directly to the point where the arrow is, no matter where the player is standing. (look at picture)
Even if I want to climb on the ladder from the bottom: I tried to put the are higher. And if I climb on it from the bottom, the player "jumps" to the top directly...