Black lines when minimizing
 

Ok, not sure if this is the right area, but anyway.

Ok let me explain the situation.

I am trying to run FVWM. Now when I open a small window and minimize the window I have not problems. But say if I open a web browser, and I go to minimize it. I get black lines over the background. The border of the window as it minimizes. I am trying to run at 1600x1200 but I would add that i have tried 1024x800 with similar effects. If I refresh the screen they the lines go away. However another odd thing is that I can run GNOME or KDE with a 1600x1200 resolution and when I minimize there is not problem with black lines.

Any thoughts would be helpful.