I can't see a grey box in the lower right, but I can see in the menu in IE7 that it slightly pops out on the lhs - I'm guessing due to the box model differences.
In the
FreeStyle skin you can look at the code and in there is an iehacks.css file which is setup to individually target IE6 + 7 - you can also specify details just for IE5. - Using this file you need to bear in mind that ALL IE browsers will read this file.
- So using this you may be able to fix some of the dimensions problems that you are having specially for IE7
Hope this helps,