Performance problems

I have to optimise a movieclip that changes the position of an number of other movieclips.

I’ve initially implemented this by wrapping my “MOVING” code in the onEnterFrame method, now I’ve changed for a function passed to setInterval… is more fluid… but WHY?

Can you check my code, is it my algorithm which is slow? is it the implementation? is the nature of the problem?

Any hint would be apreciate