screen turns black when I press to draw

I have a Toshiba Tablet with Windows 7 and Toon Boom Studio 6.0. When I press my stylus on the drawing window, a big black rectangle appears and covers up what I am drawing on.

Please advise.

The display issue could be caused by graphic card settings.
Please go to Edit/ToonBoomStudio > Preferences > Display
and change the render type.

If you still get the black rectangle, kindly mention your graphic card model.