Strange cursor

Hi

I made a custom cursor - namely “cursor_mc”.
There are also 2 movie clips on my stage, - “but_mc” and “block_mc”.
When but hits block, it should play frame 133.

My question:
If I click on but and drag it to block, everything works perfectly, but when I click on but and release it somewhere else (not on block), my cursor disappears.

Why would something like this happen?

My code:
stop();
Mouse.hide();
cursor_mc.startDrag(true);

but_mc.addEventListener(MouseEvent.MOUSE_DOWN, startbut);
function startbut(event:MouseEvent):void
{
but_mc.startDrag();
}

but_mc.addEventListener(MouseEvent.MOUSE_UP, stopbut);
function stopbut(event:MouseEvent):void
{
but_mc.stopDrag();
if (but_mc.hitTestObject(block_mc))
{
gotoAndPlay(133);
}
}

Can someone please help me?

Thanks