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First I couldn't identify your problem, as I use the more secure and standard compliant Firefox browser, but can now see it in IE, so this is an IE only problem!
And I'm not sure where the problem is, but just change the background colour of td#headerlogo from #ffffff to #b1c5d6. You will still have the border, but it will look estheticaly more pleasing (sorry I don't have more time to look into this, but maybe someone else will come up with a better answer
, for the time being this should help you out though)