* List all the ports on the 780 GTX SC
* How is the monitor connected to the video card?
* Using what cabling?

I think you need to test older video card drivers.
335.23
http://www.geforce.com/drivers/results/73780

334.89
http://www.geforce.com/drivers/results/73218

* Download/save the two Nvidia drivers to the windows desktop
* Double click the oldest one first 334.89
* Click AGREE AND CONTINUE
* Click Custom (Advanced)
* Click Next
* Check all especially "Perform a clean installation"
* Click Next
* If you get a message about, "not passed Windows Logo testing", click Continue Anyway
* When done, click RESTART NOW
* Retest
* If still no go, install the 335.23 the same way and retest

* List all the ports on the 780 GTX SC

DVI-D, DVI-I, Displayport, HDMI

* How is the monitor connected to the video card?

Mini Display port to normal display port , mini side in monitor

* Using what cabling?

Supplied dell cable Mini Display port to normal display port

I tested older drivers and it did not resolve the problem. Also, when changing the resolution in displayport 1.2 mode it doesn't scale the image, just displays it 1.1. I checked the settings on the monitor and it was set to 16:9. Whereas in displayport 1.1 mode it does scale. Is this normal? is the image supposed to scale up in displayport 1.2? Please help...I have A01 revision. 

Here is a screenshot of the options I get for screen resolutions when using displayport 1.2

http://imgur.com/efKU9nr

It sounds like you are connecting like this =
780 GTX SC DP out to Dell DP to mDP cable to U2414H mDP in #3

Test in this way =
780 GTX SC mDP out to Dell mDP to DP cable to U2414H DP in #2

Yes tried those ways as well, doesn't make any difference. 

To rule out the monitor, is there another computer to test it on? Or a different video card to install in that computer?

I tried it at work and it had the same issues. Keep in mine this is only displayport 1.2 with this issue. 1.1 seems to work. Looks like a lot of people are having problems with this monitor. Is it possible that the Nvidia driver is at fault? Can you confirm that you're able to see normal resolutions using displayport 1.2 and the 337.88 driver, using a 780GTX or similar? And that the image scales. Any info would be greatly appreciated. 

Is it possible that the Nvidia driver is at fault? Can you confirm that you're able to see normal resolutions using displayport 1.2 and the 337.88 driver, using a 780GTX or similar? And that the image scales. 

Any info would be greatly appreciated. 

Video card at work is GTX 770 4gb with the 335.23 Nvidia drivers. The revision number is A01 and the serial number is: CN-0WWRHC-74445-42R-087L

Can you please just confirm that you're able to see normal resolutions using displayport 1.2 and the 337.88 driver, using a 780GTX or similar? I really don't want to have to send the monitor back

There have been success as well as failures with these video cards. Try the 337.81 driver:

http://www.techspot.com/drivers/driver/file/information/17620/

I installed this driver but still can't see the normal resolutions when using displayport 1.2. Please can you confirm that this monitor does show these resolutions when using any Nvidia graphics card. Are you able to test this? I can't find any information about this on the internet. Chris, can you confirm?

We can only confirm it works on the Dell OEM video cards in our Alienware Aurora-R4 desktop. We do not have the retail branded cards in our lab.