Text rendering artefacts in OpenGL, with some combinations of flags, sizes and transforms

Text rendering artefacts appear with the OpenGL rendering system, when Antialiasing flag is on, with some font sizes, and with some transforms.
Here is a way to reproduce it. Sorry I had a hard time isolating the bug.
I have tested with Qt 4.6.0 and the bug was not there. I have tested with 4.6.2 and 4.7.0-Beta, and the bug was there in both versions.
It seams to be NOT the same bug as issue #7108 since I could not reproduce it with 4.6.0 while issue #7108 is marked as affecting that version of Qt.
I tried it with two different versions of video drivers and the bug was there with both (I am using an NVidia GeForce 7500 GT)