GraphicsView + OpenGL based drawing of textures fails

Platform: Mac OS X , tried 10.6.1 and 10.5.8
Regression in: Qt 4.6.0

When I use an opengl widget as a backing buffer for the qgraphicsview viewport - resizing the window causes visual artifacts to be shown.

Test case:
1. compile and run the attached example app on mac.
2. make the window slowly larger by resizing it with the mouse, you'll notice on the right and bottom edges that the artifacts can be seen during redraw.

Note that when you make the window small again (again, just using the mouse here), and then make it larger - the artifacts do not appear until the window exceeds its previous maximum size