This won't remove the problem, but it might help us help you:
Open the console (t), then type (without quotes ofc) "/maxtexsize", hit enter, type "/hwtexsize" and hit enter again. You can't read the output in-game, but in the terminal (the black window that opens together with AC), you should see two lines starting with "maxtexsize =" and "hwtexsize =" (or an error message if you made a typo :P). Post the values here.
Open the console (t), then type (without quotes ofc) "/maxtexsize", hit enter, type "/hwtexsize" and hit enter again. You can't read the output in-game, but in the terminal (the black window that opens together with AC), you should see two lines starting with "maxtexsize =" and "hwtexsize =" (or an error message if you made a typo :P). Post the values here.