Movieclip rollovers not working on different frames

Question

I'm creating an interactive that consists of 3 maps, each on its own tab. On each map, there are various circles representing data for a particular city.I want the circles to display a pop-up containing text when you roll over each one. Since I don't want the plain old buttons, I'm using 2-frame movie-clips, where the second frame represents the mouse-over state and a text box fades in as follows:
mntextbox2.addEventListener(Event.ENTER_FRAME, fl_FadeSymbolIn_4);
mntextbox2.alpha = 0;
function fl_FadeSymbolIn_4(event:Event)
    mntextbox2.alpha += 0.1;
    if(mntextbox2.alpha >= 1)
        mntextbox2.removeEventListener(Event.ENTER_FRAME, fl_FadeSymbolIn_4);
This all works fine, and I can get multiple buttons working on the first tab (frame 1) by grouping them all into a movie clip, as follows:
buttongroup.buttonMode = true
buttongroup.addEventListener(MouseEvent.MOUSE_OVER, onButtonOver);
buttongroup.addEventListener(MouseEvent.MOUSE_OUT, onButtonOut);
function onButtonOver(e:MouseEvent):void
    e.target.gotoAndStop(2);
function onButtonOut(e:MouseEvent):void
    e.target.gotoAndStop(1);
The problem is when I try to use the same or a similar with a different set of buttons on the second tab (frame 15). I put a similar set of actionscript on frame 15. The buttons seem to accept the buttonMode = true command, but I absolutely cannot get the rollovers to display. I've tried using different function names for the MOUSE_OVER and _OUT events, to no avail. I get no errors and nothing shows up in Output -- it just acts as if there's no rollover to display.
Do I need to somehow put all the AS on Frame 1? Is it an issue related to ENTER_FRAME in the rollovers? Many thanks.

Answer 1

Is there any relationship between buttongroup and mnbuttontab2?
The only code you should need in frame 15 for the rollover/out should be...
mnbuttontab2.buttonMode = true
mnbuttontab2.addEventListener(MouseEvent.MOUSE_OVER, onButtonOver);
mnbuttontab2.addEventListener(MouseEvent.MOUSE_OUT, onButtonOut);
as they should be able to use the same functions from frame 1 without rewriting them in frame 15.
Have you tried putting trace() calls in your event handler functions in frame 15 to see if the functions are getting called?