Windows 7. Have you tried disabling visual styles? Why are the windows curved even with visual styles disabled? No other programs have this problem.
System Properties - Advanced - Perfomance - Settings - Visual Effects
I have everything disabled except for show thumbnails instead of icons and smooth edges of screen fonts.
Hmm... I enabled "Use visual styles on windows and button" and the problem still exists. There is a small region on the top right and top left corners of the window where if I click the app loses focus / clicks don't count there. It is pixel perfect with the curve - and the curve still shows when maximized while other programs become rectangular?