Button demo not working properly in Firefox 2

I was going over the button demos at http://jqueryui.com/demos/button/ in IE6, IE8, FF2, FF3 and Chrome 4 and discovered that the anchors, radios and checkboxes are broken in FF2. I had assumed it was the theme and/or the page itself but the issue is still present when I change themes and tested it on my own page.

The full FF version number used is 2.0.0.20.