Comment 7 for bug 1241988

There seem to be another user on nvidia binary driver also with issues:
http://www.riverbankcomputing.com/pipermail/pyqt/2013-October/033379.html

And he got it working with nouveau driver.
http://www.riverbankcomputing.com/pipermail/pyqt/2013-November/033384.html

So the commonality might seem to be the nvidia binary driver.