Does anyone have any issue with Dell 2913wm with 2012 MBR ?

I just bought dell 2913wm 29 inch monitor and trying to set it up with my mac. I have two macs- one is 2012 MBR that and a 2011 Mac air. I am using the displayport to mini-displayport cable that comes with the monitor.

The monitor is working properly with my mac air. I can use the maximum resolution and everything looks perfect!

However with MBR, I'm not getting the expected output from the monitor. The quality of image gets worse with pro- which is weird. The texts looks blurry (for all resolutions) and broken. I'm not sure what might be the reason behind this.

Did anyone face this kind of issue? Should I try to use a new cable or is there anything else I should look at?