ActionScript 3.0 :: Rollover Button Won't Play Nested Timeline

I'm creating a website by splitting up the main timeline into the different pages of the site. I'm trying to make a dropdown menu on the 3rd frame. On a layer called buttons I have a button with the instance name patientnumberbtn. I want that when you roll over this button is tells the menu to drop. The movie clip for the menu is nested on its own layer of the main timeline. I would like to play this nested timeline, (the drop down menu has masks and other animations that are moving around). This movieclip that everything is nested in has an instance name of patientnumbermenu. Here is what I am using for code.

patientnumberbtn.addEventListener(MouseEvent.MOUSE _OVER,patientnumber_over);
function patientnumber_over(event:MouseEvent):void
{
patientnumbermenu.play();
}

When I run it there is an output error #1009 but it still lets me proceed. When I roll over patientnumberbtn, nothing happens. Within the patientnumbermenu I have stop commands to prevent it from playing when we first reach frame 3 of the main timeline. I've removed these commands and the patientnumbermenu will play even though the commands used to get to frame 3 is a gotoAndStop(); command.