I have an ubuntu server running vnc4server and gnome-session.
When i log in remotely using VNC, it appears that the windows key is stuck. This occurs with multiple VNC clients (ultraVNC/realVNC on windows) and I have tried from other boxes.
Having the windows key stuck effectively disables using up/down, since windows key+up and windows key+down are bound to maximizing and minimizing whatever window you are on.