I had texture drawing problems with my 4890 and 8Gb of RAM. I did the trick mentioned here a couple pages ago and reduced the maximum memory from System Configuration to 3328Gb. No issues remain anymore.
Although ArmA2 runs now without problems, I'm wondering if there's any other ways to get rid of this problem? I'm not considering RAM reduction as a viable solution. This is something that really needs to be fixed in the next patch.