Windows 7 Browsers Ignoring DIV height 100%

I am using the jQuery UI.Layout plugin and on OSX in Chrome, FF, and Safari, all is hunky dory. However, on Windows (7) on Firefox, Chrome, and IE8 I am getting the following:

The layout container "DIV/#project-container" has no height.

So the DIV isn't visible. My div is very simply defined like so:

<div id="project-container" style='height: 100%'>
....
</div>

So what gives? If I say height: 100px it renders. Why is this only happening on Windows browsers (other than the obvious windows bashing reasons).

It's usually a good idea to make sure that you apply 100% height to your body & html tags as well:

html, body {
    height: 100% !important;
}