I switched to this other theme for the time being, because the modified one was rather broken in IE6. I rather liked the other one, so I will hopefully find some time to figure out what was the problem. The theme I had based it off of also appears to be behaving poorly in IE6, so I’m not sure its directly my doing.
By the way, if you are doing web development on a non-windows pc, you might be interested in this site:
which lets you preview how the page will render in IE6 or IE7 (seen on lifehacker.com).