Right, third time lucky. I missed a vital step out of the instructions last time.
As well as removing the vertical-align: top from #mainWrapper {} you also have to ensure that there are no spaces or new lines between the end of the img tag and the </div> tag. i.e in you HTML you need...
HTML Code:
<img src="index_files/logo2.gif" alt="" usemap="#logo2" style="border-style: none;" height="222" width="750"></div>
IE has a habit of rendering white space (including carriage returns) after img tags. 
Hopefully that should fix it.
Christian.