@Silgidorn
I've also solved this issue by installing Catalyst 10.12 on my iMac. For this, I've downloaded and installed
DH Mobility Modder.NET, dowloaded the latest Catalyst display drivers for XP 32-bit (
individual package, not the complete driver set). I've extracted but not installed these drivers on my computer (ie click Cancel when the real installer starts), follow the hint
here then use DH Mobility Modder to mod the drivers. For the installation, I've performed a manual install from Device Manager > Properties for the graphic card and using Have Disk option.
For the moment, all seems to work fine but I'm still reluctant to use non-official drivers.