With the Nvidea cards going SLI all the monitors must be on the same type of output ie. HDMI VGA or DVI ports for it to work. The reason is the refresh rate must be the same on all 3 monitors.
LawnDart
Really? I was under the impression you could mix DVI and HDMI, just as long as you only had two monitors per card. At least that is the case with ATI cards, perhaps it's different with nVidia. On my card I can set one monitor to 45 Mhz and the other to 75 Mhz and all is gravy (except that the one with 45 Mhz is choppy...). Mycurrent set up is 75Mhz on the left, 60Mhz on the right, or 75Mhz on the left and the HDMI to my TV at 60Mhz on the right.
From what I understand, each graphics card has the ability to do two different clocks (one clock per monitor). That's why with SLI you get 2 on one and 1 on the other card. You now can get 3 (or more, I think there is a ATI card with 6 display ports on it...) on one because Display Port gets rid of the need for the graphics card to provide the clocks, that's all done onboard the monitor (or active DP port) now.
I'm sure the nVidia cards with display port have the ability to do 3 monitors one card as well.