Firefox won't do percentages

I have a client who wants a scalable Flash movie that adjusts its size according to the size of the browser window.

This is easy to do by adjusting the Publish Settings for width and height to percentages, rather than pixels.

It works well in Safari and IE, but Mozilla (Firefox) presents it as a very small image, roughly 1/3 the size of the pixel count of the original screens.

I’m adjusting for this by coding to pick up the browser, then assigning fixed pixel counts for the width and height if the browser is Mozilla. This is OK, but not ideal.

Is there any way to maintain the percentages with Mozilla?