New aluminum iMac 24" - texture problems

[Buckie]

Guys!
I've written by email but got no response.
Anyway, is there a way to make the game look as it's supposed to be?
I have numerous problems with textures in different places - from annoying flickering to completely missing or misaligned textures.
When the focus shifts to some object the screen gets blurry (I guess that's intended) and divided in two halves and flickers. Yuck. Is there a patch in the works or some workaround for that?
I'm on 10.5.1 now.
Would be glad to provide any further info if required.

Thanks for a truly great game, but texture problems ruin it big deal. Hope you'll have it fixed.