Personally I have not see Windows 8 yet ( although the Technical team are having a play with it).
As you know XSitePro creates industry standard HTML, so this would seem to be an issue with how IE10 is rendering a standard web page.
Microsoft will have to fix this or most of the worlds web pages will look wrong in their browser.
The usual differences between the browsers these days is how the padding around images and tables are handled.
Please check the padding for the different Panels and any content you have too.
Try setting the padding to 0px as a first test.
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