Infinite menu stop on mouse out

Ok, I’m about to loose my mind, I hope there is someone out there who can give me some pointers.

So, i have an infinte menu (actionscript (AS2) posted bellow)

When the mouse moves out of the movieclip over or under, it stops. However if i drag the mouse to the right or left of it, it just keeps on speeding up.

Anyone got a clue?

onClipEvent (load) {
var xcenter = 280, speed = .01, decel = .90, accel = 0;

}
onClipEvent (enterFrame) {
var distance = _root._xmouse-xcenter;
if (this.hitTest(_root._xmouse, _root._ymouse, true)) {
accel += distance*speed;
}
_x += accel *= decel;
if (_x>0) {
_x = -2255;
} else if (_x<-2255) {
_x = 0;
}
}