In Windows 7 if the Aero GUI is switched on and the Xsheet scrollbar is used, the Open GL view becomes temporarily disabled (either Gray or Black). To restore the view, click on the drawing in either the Xsheet or the Timeline.
Disable the Aero GUI. By default, Windows 7 uses an Aero theme. You can temporarily disable Aero on Windows 7 by choosing a non-Aero theme for your desktop.
Here are the steps to turn off Aero on Windows 7: