Try 1280*1024. Before you say "that's utter madness, 1280*1024 is 5:4 and my screen is 16:10", in the setting below resolution in the 360 settings you can set the aspect ratio to 'wide' and then the aspect ratio is correct. It's higher res than using 1280*768, and it doesn't do any vertical upscaling so the picture quality is better.