I ran a further check in software rendering mode, and the game runs "normally". There is no difference in the console log. So, all in all, things are better and the game runs very will using internal rather than GPU generated rendering. The interesting thing is that this version of the ATI/AMD fglrx driver actually can handle this game in 1920x1080x32 DVI mode. When hardware rendering is on, however, the frame rate goes to something around 1 per second or longer.
