This is a little tough to explain, so I'll include pictures. Windows Live Messenger 8.0 (Build 8.0.0812.00) has a feature that allows you to hide the menu bar. When I have that enabled, my Messenger windows, seemingly randomly, develop an extended top bar where the menu bar used to be. If I move my mouse anywhere on that area, the cursor becomes the vertical double-arrow for stretching the window size. It's as if WindowFX only partially recognizes that the window isn't as big as it thinks it should be?

I sure wish I could explain this better, but let's try this:

Messenger window with menu bar enabled (everything works normally):





Messenger window with menu bar hidden (note that this is not edited; this is an alt-prtscn of my Messenger window with a portion of my wallpaper absorbed as part of the window):