(NetAdvantage for ASP.NET 2010 V1)
As an FYI in case anyone else runs into this. I ran into an issue with the Office2007Blue theme and the WebExplorerBar.
The itemHover image (igeb_ItemSelectedBg.png) was not the right size. The image would not fully cover up the text of the menu item. After comparing this file to the file in the other themes, it was several pixels too small. I edited the image and sized it to 30px. This resolved the issue.
I saw that this issue is internally fixed and will not be a problem after you get the first service release for 10.1.