Dell U3011 30" connection problem

Hi everyone.

I have a short question. I just bought 3x Dell U3011 30" monitors and i have connected them to my computer via the DVI ports.

I wanted to use the Display ports but when i connect any of them to the Displayport on either of my graphic cards.

There are no connection. I have one nVidia Quadro 4000 and 1 Geforce GFX 590 both with many Display ports.

But i can't get any one of them to connect when using the Display port. I used the included display cable and just connected

one end to the monitor and the other end to the graphic card. Nothing ?

And when using DVI ports. Everything works. But i want to use the Display ports because the Quadro only have one DVI port

and i need to connect 2 monitors to the Quadro 4000 where right now i have 1 connected to the Quadro 4000 (DVI) and the

2 other monitors connected to the Geforce 590 (DVI) sucks :(

I can't figure out why they doesn't work with the Display cables/ports ???? I'm using Windows 8 Pro 64 bit in a totally new build

Workstation i7 Extreme CPU.

Please i need help ASAP to finish some work i have. I hope someone can help me here.

Thanks a lot everyone.