If that doesn't work, I saw a video where someone was changing settings, from low to high and back, and it wasn't doing anything, but he forgot the "Texture resolution" slider. Knock that baby up above 0 (100% is really where you want it) and see if that helps too.
Also, Dasius, there's a bug that makes it not save settings when going back and forth from sandbox mode. Maybe each has its own settings? Or something, I haven't tested this out thoroughly.