OpenGL 1.0 ATI Drivers are totally unstable.
Quitting Graphics Calc 1.1 causes desynch in my scan rate (1024x768@100hz) forcing reboot.
Sherlock freezes machine when ever the spinning arrow begnings.Q3Test cannot restore desktop after quitting game.
I traced down this issue to the ATI Drivers.
The ATI Drivers that come with MacOS 8.6 are much stabler. The one that come with OpenGL 1.0 beta are stable (and are newer than the one in MacOS 8.6 archive).
If you switch drivers in any of these two - please remember to remove the ATI Driver update extention (last one in the ATI list)
otherwise your machine will hang.
Hope i helped.