framebuffer repaint problem

hey guys,

I have a problem considering repainting. I divided my Widget to 4 viewports and when repainting i update only the changed viewports.

To do that i use glScissor before i clear the framebuffer so the rest of the framebuffer is intact.

It works perfectly on my machine with nvidia 7900, but, on other machines an annoying flickering on the other viewports occurs.

Is there something i am missing here? is there something that should be enabled that is handled differently by different implementations?

I would disable scissor, call glclear, then enable scissor section by section and draw. The last step is to swapbuffers.