I've spent some time looking at this and I've tested IE against several other sites running the same version of Vendor Tools to see if they are centered. On all the sites I checked only your installation is showing as not centered.
In investigating further I ran the URL (
EN World D&D / RPG News - Powered by vBulletin) through a Tidy utility (
HTML Tidy Online) to determine if there is some HTML that is confusing IE. Usually when I see different behavior between browsers it is due to some HTML tagging issue (ie - broken table cells, form tags, etc.).
When I run your link through there are some usual warnings you can ignore but the ones that concern me are those showing div tags outside of the body and Tidy thinking it needs to insert an implicit <body> tag for the page. Given this I believe that with some use of the Tidy utility you can resolve this issue in your style. I would suspect that most of the changes needed will be found in the headerinclude and header templates. Obviously if this is where the changes are made it will benefit your entire site as Tidy is reporting similar problems when I go to visit pages like your FAQ area (
EN World D&D / RPG News - FAQ).
If you can get these sorted out I would expect that IE will start to render the map centered as expected.
Hope this helps!
Mark