I'm using 1GB and it works fine (with occasional FPS drops, but nothing dramatic). More memory might help, but I doubt it. Seems like the shader is not being compiled successfully. Not sure why that is happening. Did you already try to play without the new shaders? I think you were able to disable them either in the options or with a key shortcut. Can't remember and can't install the game on this computer. Devs might be able to help after seeing those errors, since they are the ones who know how the game reacts to this kinds of errors.