Hi Pascal,
I got the same problem.
2013/7/30 Pascal d'Hermilly <pascal@dhermilly.dk>
Maybe you want to play with /etc/sudoers... adding the following fixes the behaviour Defaults env_keep +="QT_GRAPHICSSYSTEM"
(and running : service sudo restart)
Can you copy/paste the content of your /etc/sudoers? I just tried to add this line after Defaults and doesn't work for me. I also tried to comment Defaults