When it is a dual link DVI.
I just got a Dell U2711 monitor and it looked awful. It looked like there was a DPI or resolution problem. I was wondering if the graphics card was too old or some other driver/configuration problem.
Nope, needed to use a Dual link DVI cable (thanks http://photography-on-the.net/forum/showthread.php?t=857897). How can you tell the difference? Dual link is printed on the cable.
Would have been nice if Dell included in the 'monitor setup' cheat sheet a little note that you must use a dual link cable.