This is the second time I've heard about this issue with a GTX-570.
DKS (like almost all games) is a 32bit application, and as such it cannot address more than 4GB in total - this includes memory used by your OS (or it couldn't make system calls) and also your graphics memory. So the actualy ammount of memory the game gets is significantly less than 4GB.
My guess is that because the GTX-570 comes with (minimum) 1.25GB of ram (more in some configurations), then it's eating into the 3GB minimum that the game needs in main memory to store high textures on a Windows7/Vista computer.
If your old graphics card is <=1GB, it might be worth trying swapping it back in temporarially and see if high textures work again. Of course if this is the case, then you'd be undestandably frustrated - the GTX-570 is an awesome card, and not being able to push it to it's full potential simply because games are still stuck in 32-bit mode would be really annoying.
Finally I doubt Kein's suggestion will do any good - simply preventing it from overwriting the config won't stop it switching to low textures - it has obviously detected an issue and already switched to low textures before it tries to update the config.
Even if I'm wrong about the memory issue, it could still be something related to the 570 - it seems more than a coincidence that both posts on this issue were using that specific card.
Has anyone else got the game to run high textures with a different (>1GB) card? I'm very interested in this topic because I'm thinking of upgrading my old GTX-295, and I need to stick with NVidia because I use 3D Vision.
