In modern Ubuntu versions (11.10, 12.04) there is an additional style for Ubuntu font called 'Medium' it's slightly thicker than a 'Regular' style user by default.
The problem is that all QT apps just suddenly start using that 'Medium' style, instead of 'Regular' which is used by default in all GTK apps.
How to fix this without removing /usr/share/fonts/truetype/ubuntu-font-family/Ubuntu-M*.ttf
?