FAQ/Aero and Hidden Floating View
From VFXPedia
There is a bug under Windows Vista and Windows 7 that can cause the header of a minimized window to disappear when minimized due to the Aero and Off-screen Compositing it does. You can try to disable this via the Control Panel\All Control Panel Items\Performance Information and Tools\Adjust Visual effects\ and then deselect the "Enable desktop composition"