I can't see the project above, because I've done a hard drive format and haven't installed VB yet, but I guess you're having the same problem as what I had in the topic below.

http://www.vbforums.com/showthread.php?t=507336

Simply put a Picturebox with a white backcolor on the TabStrip and make the backcolor of the Frame white as well. You will only lose the gradient backcolor of the TabStrip, but I don't think anybody will notice (see the difference between first and third picture in the topic above).