MC's randomly shifting within flash nav

Hi all,

www.h2sr.com

If you click on the flash nav in IE7, occasionally the logos within will shift hard to the right. I can’t seem to come up with a pattern for this, but here is the very basic script on each of the MC’s:

this.onEnterFrame = function(){
	if(rewind == true){   //if rewind switch is set to true play backwards
		prevFrame();        // play backwards
		_parent.prevFrame();
		skewed_mc.prevFrame();
	}
}

this.onRollOver = function(){
	rewind = false; //set variable (or switch) that decides wether ot not to play backwards...
	play();    // play this movie clip.. (grow the button(tween))
	_parent.play();
	skewed_mc.play();
;
}

this.onRollOut = function(){
	rewind = true;    //set or rewind switch to true so it will play backwards...
}
stop();

A level above that code is a simple getURL on one layer:

strip_mc.onRelease = function(){
	getURL("?page_id=490");
}

As well as a layer with a stop on frame 1 and 10.

I have been pulling my hair out like crazy over this… any inklings of an idea would be hugely appreciated.

Thanks!