Dano, finally got to this for you.
Go to your css and make the following changes to the #maincontent
Code:
margin-right: 190px;
margin-left: 180px;
This allows 20 pixels additional for the centre content. It may look lousy from a display perspective but see if it pushes the form back up to where it should be in ie6. If it does we can make a couple of other changes to the CSS to get it looking right again.
The second thing is I don't know if it is where you were playing there is an unnecessary opening div tag at line 179 right after you open the centre div for content, so delete that too if it is in your live site.
Let me know if this fixes the problem and then we can tidy up your css from there.
Colin