It is indeed an IE issue ot more better a mixed issue.
I also have seen certain problems with plugins.
They are all probably designed to have a nice view in Firefox.
But with this kind of design you get a reversed problem.
If you only design under IE or FF Pages or categories do not show up well under FF Op NS IE and so on.
Also when you only wish to design under FF for example certain content is pushed downbelow the way you normally want to show your page.
IE as well as FF has some differences in showing pages.
But if everything has been done well pages are looking almost the same on different browsers.
FF aswell as IE have certain things which I call bad habbit.
Thats why its very important to use more browsers when you design.
I also have a link somewhere on this forum to a CSS file which already is improved a little bit but still needs a lot of improvement but the basic design is from someone else.
There are huge difference’s for example under IE and FF.
Under certain conditions everything looks fine on both site but suddenly you get surprised and everything is pushed down again by IE and or FF.
The real problem is the basics are interpreted different in different browsers.
And is also related to competitive behaviour.
If the basics do not get the same level it always will be difficult to give everybody the same look.
For now the only advice is and remains to design for more then only one browser.