I was just looking at the source of your site, and you've got a couple of background images that are 2000px wide, so that's what's preventing your menu from wrapping.
I suppose I could something similar on my site, but my preference is to have the individual menu items wrap, so that the whole menu bar would become thicker (higher - bigger from top to bottom...)
It doesn't really matter how many items are on the menu, because at some point if the user reduces the size of the browser window far enough, or increases the size of the font (something I do all the time, which is why this is a problem for me) the menu bar will run out of space and wrap.
BTW - have you looked at your site in Firefox? There isn't any bottom scroll bar when you reduce the size of the browser window or increase the font size. The scroll bar appears correctly in IE.
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