dual link external monitor problem

I bought a brand new Dell U2713H monitor (resolution is 2560px wide) so I had to get a dual link adaptor. I plug it into my Macbook pro 17-inch, Late 2011 and it works beautifully for about 10 minutes and suddenly the screen turns to static and i get a dvi symbol on top left. i then turn off and on the monitor and i get another 10 minutes. I was sure it was a faulty dual link cable - but i am trying the monitor on a macbook air and it is working perfectly.

any idea what the problem can be? perhaps the AMD Radeon HD 6770M 1024 MB card is not good enough? but i was told by apple support before i bought the monitor it is fine as long as i use the dual link cable.