I am using the following code for my iframes:

<iframe frameBorder="0" height="100%" width="100%" src="THE.URL.COM"></iframe>

However, when you go to my Desktop sample and click on any of the icons it doesn't load the iframe at 100% height for some reason.

You can see that here:

zazavi.com/desktop/desktop.html

If anyone could tell me what I am doing wrong, it would be greatly appreciated. Thanks for your time!

It looks fine to me. The one thing I can think of, though, is to set the height to 100% on the html and body tags aswell, if you havn't already.

html, body {
   height: 100%;
}

EDIT:

Oh, now I see what you mean.
It seems you have a padding of 5px, in this part:

<div class="x-panel-body x-panel-body-default x-layout-fit" style="padding-top: 5px; padding-right: 5px; padding-bottom: 5px; padding-left: 5px; left: 0px; top: 25px; " id="ext-gen1356">

I did end up getting this to work and it loads in FireFox for me but in Internet Explorer I am seeing a gray box with no scroll bar loading on the right-side of the frame... Any idea what's happening with that?