Okay, this is strange. The default theme for clug.org, "pushbutton" has stopped working in IE, but not firefox. It was working 3 weeks ago when I was doing a lot of stuff with the auctions. And no important files have changed since then. Maybe you can figure it out! Here are the steps I've taken...

Determined the Error is Comes from the Style Sheet

I saved the source for both versions of the front page, and opened them up in IE. I then copied lines one by one from the version that worked to the version that doesn't. The line that causes the failure is the line that loads the cascading style sheet.

Clue: One Style Sheet Gets GZIPPED

I used "wget" to fetch both .css files. The broken one came across as gzipped, the one that worked wasn't. Neither one is gzipped on the server, so Apache is gzipping it.

I found an article with a patch to .htaccess that overrides apache's config file. This seemed to work, since now the .css file is no longer gzipped. This didn't seem to fix the scripting error.

If you want to compare the two files, they are:
http://clug.org/themes/bluemarine/style.css
http://clug.org/themes/pushbutton/style.css

They both validate (with warnings) on http://jigsaw.w3.org/css-validator/

Upgrade

BTW, I upgraded drupal to the current level 4.6.5 to fix the recent security flaws. No changes were made to the database, so I only had to copy the newer files.

Let me know if any oddness happens.
-Kip