The "Buddies" window has an X button in the top right corner. However, this button does not close the buddies window, but instead minimizes it. In addition, the tooltip on mouse-over says "MINIMIZE". This is inconsistent with the vast majority of Windows applications, and also with PVP.net itself -- the main window has "X" and "_" buttons (close and minimize, respectively).
Suggestion: change the "X" in the buddies window into an "_", and change the tooltip to be consistent with the main PVP.net app (something like "CLICK TO MINIMIZE PVP.NET BUDDIES").