Just got the 5870 installed and it works great...except in AA3

Game runs but horrible pop-up problem and the textures are completely hosed. An example of the pop-up, when doing single mission where angry villagers attack the communists in their village, when standing by the building where the sniper waits, only two or three major buildings show up in the town. Ground and vegetation textures are missing (vegetation completely missing).

EDIT - Problem was too much RAM (12 Gig) so have to run -winxp startup parameter.

did you do a clean re-install of drivers after install? Everytime I get a new card I always clean out my older drivers because they do cause weird effects. Also, you might delete your Arma2.cfg file (it will make a new one when you start the game). Sometimes it has problems auto-detecting your gfx card

Thanks for the tip on the config file. Will try that. On the drivers, yes, did clean them out then did a clean install of the new drivers.

EDIT: Deleting orginal config file didn't help

Have a look into the config file what it sees as your vid ram.

With my 4890 in video memory option I've to use Very High setting, or I get texture problems.
Before getting the 5870 what was your graphic card?

Here's my ArmA2 config file:
language="English";
adapter=-1;
3D_Performance=93750;
Resolution_Bpp=32;
Resolution_W=1920;
Resolution_H=1200;
refresh=60;
Render_W=1920;
Render_H=1200;
FSAA=2;
postFX=2;
HDRPrecision=8;
lastDeviceId="";
localVRAM=5959680;
nonlocalVRAM=5959680;

Previous card was a 4870 X2.

These settings don't seem to be the correct ones.
Try to set the Video memory on the video configuration menu from 'default' to 'Very High'.

I believe they just released a new driver build specific to those cards, in place of the betas they had before. See if they help solve the problem.

Unfortunately, it helped a little, but still have significant texture issues. Tried the various video memory settings, texture settings, and even resolutions and still same problem, missing textures.