Button Rollovers loading problem

[NDWest12]

I'm working on this new page, this is only a place holder page for the client to show that i can do it...however i'm running into a really annoying problem in terms of the rollovers on my buttons

The first time you load the page it works perfectly and takes you to the next page where the buttons will also work perfectly, but if you navigate back to the page the thing will pop right in

_root.aboutus_mc.onEnterFrame = function() {
if (mouse_over_aboutus_mc) {
_root.aboutus_mc.nextFrame();
} else {
_root.aboutus_mc.prevFrame();
}
};
stop();

that is the frame action

on (rollOver) {
_root.mouse_over_aboutus_mc = true;
}

on (rollOut) {
_root.mouse_over_aboutus_mc = fstartlse;
}

on (release){
gotoAndPlay(86);
}

and that is the button action

http://nickwestcott.com/example1.html

you can view it there, only 1 button is set up but if you click that and then click the button on the next page you'll understand the problem....i'm assuming its something missing or within the code