When I re-added the <div id="page-header"> to the css, IE didn't handle it very well, while FF just adjust to the error.
What I did find is that this div is too far down to close off the header stuff before loading the menu and breadcrumbs blocks.
<!-- INCLUDE menu_block.html -->
<!-- INCLUDE breadcrumbs_main.html -->
</div>
In case you don't believe me MG - the IE pictures tell the story.
