Resize on custom OpenGL widget regression

A custom QWidget subclass
http://vtk.org/gitweb?p=VTK.git;a=blob;f=GUISupport/Qt/QVTKWidget.cxx
has suffered a regression between Qt 4.5.2 and Qt 4.7.1 on Windows with Aero off (not a problem with Aero on).

Noteably, it sets MSWindowsOwnDC, WA_NoBackground, WA_PaintOnScreen.

If I resize the widget larger, it appears that some corrupted layer is put on top of the widget. If I resize smaller, the apparent corrupt layer is removed.
When resized larger, I can see a last few pixels of correct data in the newly exposed area of the widget during resize (which is why I suspect a corrupt layer). Also, if I switch focus to another application and back, the widget fixes itself and the entire widget content is correct.

If I remove WA_PaintOnScreen, the problem goes away, but another problem shows up.
If I remove MSWindowsOwnDC, the problem goes away, but that doesn't seem correct.

The problem can be seen by resizing the window of any Qt example in VTK, such as qtevents (VTK/Examples/GUI/Qt/Events).