Derived DataGridView drawing problem. Shows black regions

Answer 1

Try setting the .ResizeRedraw property of your control to true in the constructor, see if that helps.

From MSDN:

Gets or sets a value indicating whether the control redraws itself when resized.

Answer 2

Try clearing the graphics with the grids backgroun in OnPaint

Graphics g = e.Graphics;

g.Clear(this.BackColor);

Answer 3

It sounds to me like your control isn't rendering its layout properly.
Did you suspend layout at some point in your code, and then never resumelayout?

Doing so will allow your control to function properly, but not lay out all of its components properly.