Video card/monitor woes with high screen resolution

My bedroom PC needed to be retired, it was a Dell Precision 630; dual Xeon 2.8ghz CPU's w/ 4mb cache, 400mhz bus; a real screamer in its day.  Alas blown capacitors on the motherboard started to make the PC slow, odd video issues, and occasionally not boot.  Besides, I suppose it is time I finally let go of my last Windows XP machine.  This machine has an ATI Radeon 256mb  AGP video card.  That card drives a Dell 27" (2550*1440 resolution) and an IBM 21" (1600*1200 resolution).

Its replacement is a Dell Precision T5400, Xeon L5420 2.5ghz Quad Core w/ 12mb cache, 16gb ram FB-5300.  It is upgradeable to a 2nd cpu, and these "L" Series CPU's only require 50 watts of power vs. the normal 75~100 watts.  It currently has a Nvidia GeForce 210 1gb ram PCI-E video card.

While setting up the T5400 it was on a different 21" monitor running at 1600*1200 resolution.  Once moving this machine to its new home, I was greeted to see this:

That machine booted up into Windows 7, and was just fine.  Until I moved the screen resolution to its native 2550*1440, it then went pink and fuzzy again; dropping it to 1920*1080 it was fine.  I knew the monitor was fine since it ran at full resolution on the old pc.  I swapped out the DVI cable, same result.  I swapped to the VGA connector (DB15), the picture was clear but maximum resolution was 2048*1150.  Went back to DVI port on the video card, used a DVI->VGA adaptor, 2048*1150 was the result.  Switched to HDMI, 1920*1080 resolution. 

I tried five different video cards, and nearly the same results!  Interestingly the ATI based cards show properly on post, only the Nvidia cards were fuzzy and pink at post.  So I have ruled out the monitor, the dvi-cable, and the video cards as possible issues.  It was starting to look like a flakey motherboard or something else strange.

A friend of mine mentioned that perhaps I need a dual link DVI cable.  Huh?  What is this dual-link you speak of?,931-8.html
I acquired one of these Dual-Link DVI cables, and tadah!   No more pink fuzzies and full resolution!!!