I passed this to our IT guys and got this response:
"I think the issue lies in the version of IE8, this is an early build of IE8 which does not seem to support the css style that is being used, while even just later versions of IE8 seem to."
that is, this build of IE 8 is the current latest for XP, Vista, and Windows Server 2008 R2 (see
support.microsoft.com/kb/969393) - IE 7 and earlier and IE 8 for Win7 etc is fine.
Our guy found a fix that looks like the attachment - if you're interested I can ask him to post it...