I couldn't get my 1920 x 1200 resolution to function properly on my Viewsonic VX2835wm pumped through a bfg gtx285 until I found that disabling edid extensions could workaround the problem. Perhaps this is old hat news but it took me 3 1/2 days and 126 google articles to figure it out. Answer was here:
http://analogbit.com/node/23
Hope this helps someone else.