Maintaining flash movie size regardless of resolution

It seems I've run into a problem while trying to embedd a flash application type thing into this website I'm trying to make. The flash application is only the test of an image gallery I'll be putting on. When I put the flash app on the website, with my resolution (1152x864), everything was fine, as you can see in this image below:



but when I change the resolution, the flash app's buttons overflow the borders,
as you can see in this image:



has anyone got any ideas on this? I've tried making a javascript that detects the screens resolution and changes the size accordingly, but that method just messed up the rest of the page.

Here's the code for the flash app:

<div class="gallery">
<object width="550" height="400">
<param name="movie" value="somefilename.swf">
<embed src="gallery.swf" width="800" height="400">
</embed>
</object>
</div>

Code (markup):

And the CSS:

div.gallery{
       margin-right: auto;
	   margin-left: auto;
	   padding-top: 3em;
	   width: 50em;}

Code (markup):