A lagging Dell u2713h display connected to MacBook Pro Retina

[Duzevert]

Hello everyone!
Posting here for the 1st time.

I need some help with this problem:
I play WoW on MacBook Pro Retina with Dell u2713h display.
Firstly I had some problems with the colors because Macbook thought that Dell was a tv-display, but after buying the right cables the problem was solved.
Now the colors are great, but there is some kind of delay on the display image. When I move my character it moves something like a 0.5 sec after pressing the key. Turning the character with the mouse cause the same problem -- a 0.5 sec reaction. But the cursor of the mouse moves normally, without any delaying.

Has anybody the same problem?
Is there any solution?

Thanks!

[glo]

Go through the monitor's settings and see if there's something like "TV mode" enabled. Try to disable any kind of post processing.

[Christendom]

is this the 15' or the 13' MBPr. The 13's lack that dedicated vid card and I could see it lagging on a larger display. They're barely powerful enough to push its own screen.