Oh man that's bad luck to have such a great new card and a glitch with one of your favoite games.

If your looking for a complete list of drivers regular Cats and Omega (the best ATI modified) try here.
http://downloads.guru3d.com/

Secondly the setting he is refering to is "radeonHackAmbientColBug=0" but this is only in Gothic 2 ini not Gothic 1.

Is your Cpu a Dual Core or Dual/Quad processor?

My guess is your best chance is a Modified Omega Driver, since he fine tunes the drivers specificly for games and he has an execellent reputation, it's possible he has caught the glitch.

Personally I would try a driver from maybe June and then September, if the newest Omegas 6.9 here, http://downloads.guru3d.com/download.php?det=1492 don't work.