Odd bug on main menu

A site I am developing has an odd bug on them menu.  Please look at the main / top menu on iveac.org See the little white areas on the menu items "Forums" and "Events" - what is that? - a corrupted file or something?  I had one before, removed the menu item, and now I have two.  Anyone know what I should look at to fix this?

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Thanks

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Rob

I seem to be getting it in IE and a little in Chrome, but not FF - can anyone else see it?  I uploaded a new banner and now it is blocking part of the banner.  If anyone knows what might be causing this, please let me know.

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Rob