the aticonfig --buildpkg
So while I had some hard-lockups when using the 3D-acceleration, when I turned off the fancy Desktops-Effects, everything became fine. I have to see if it has to do something with the overlay-mechanism, since I catch this hardware-cold only under certain circumstances (i.e. switching video into fullscreen).
But instead of looking to find the bug, I thought, I would rather write about it. After all. If you don't care about fancy wobbly windows and rotating cubes, you are fine. The question is, why would you want a Radeon 4670 at all?