Speed Up WordPress in Internet Explorer?

We just created a new website using wordpress and it loads incredibly fast in Firefox, but loads very slow in Internet Explorer. We’ve already reduced the size of images, removed unneeded plugins, modified the PHP header and footer, implemented Super Cache, upgraded our server capabilities and many other measures. We just can’t seem to nail the reason for the slowness using IE. Again, it is lightning fast with Firefox. Any ideas? Anyone else run into this problem? Thanks for your thoughts / ideas.