I have what I consider a solution in regards to your "tiny rectangle" problem, Toasters.
If you look at the WindowSkin file closely, down in the bottom right corner of the horizontal line section (left side of the color blocks section), there's that small rectangular spot that's giving you issues.
So, my advice is to open the WindowSkin in PhotoShop.. or some other form of image editing software.. and patch up that tiny blank space by continuing the lines across.
Hope that helps ya.
-Heart of Shadow-