Nested buttons

Hi there,
I’ve created a flash swf that allows you to pan and zoom a movie clip, but it has nested buttons with mouse over effects.
When I scale the movie clip it works fine, but some of the buttons are not responsive or the activation area has moved to the side.

The majority of the buttons seem to work when completely on view…

Is there any reason why the buttons reaction would be offset by the re-sizing of a MC?

Any help on this would be great

Using AS3

R.