When is DVI not DVI?

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.