On one Windows XP machine, all of a sudden, Outlook lost all of it's 3D attributes - all of the icons are now flat, the colors are muted and the buttons have no shading (almost as if it switched modes to something simple/lower resolution). I have made no changes - the screen resolution is the same. Even stranger, when I open any menu boxes, like Options, all the shading/3D/colors are there. What happened? How do I fix this?