Window is redrawn inside the OpenGL area instead of the whole window

We have a “kiosk” system running on windows XP.
The interface involves an OpenGL graphic area inside a standard window.
The software is written in Visual Basic 6.
This system has been in use for more or less 10 years with various hardware along the way. One by one the hardware is phased out and we constantly have to find new motherboards to fit our system requirements.

The most recent motherboard is “iBase MI957-i7” with an integrated Intel graphic (i7).
This is where the problems start.

90% of the time this works fine, but sometimes the window where the OpenGL area resides is getting drawn inside the OpenGL area instead of over the whole window, so there will be a “window inside the window” so to speak. Next refresh will draw it correctly, and the next is again wrongly. So the screen will be “jumping” up and down. If you drag the window in the title bar the window will “tile” inside the OpenGL area.

I have not been able to figure out what triggers this behaviour or if it is temperature related. Sometimes it happens when moving the mouse over the area, sometimes it is jumping by its own.

I have downloded the latest drivers from Intel (although drivers for XP is not so fresh).
The supplier has no solution, suggesting incompability with the motherboard requirements.

So my final hope is this forum. I am not sure how to label the error and if I am in the right section at all.