7609WU, DP does not connect to laptop DP

Presently I use a Dell Latitude E6500 connected to two Dell 7609WU projectors for 3D projection with a Matrox DualHead2Go DP box.

In order to get smoother execution of slideshows I have bought a Dell Precision M4800 laptop. However, the connection between the DP ports on the laptop and the projectors does not work, even when the laptop is connected to one projector without the Matrox box. When trying to connect (Fn F8) the display on the laptop changes to 1950x1200, but the projector screen is still blue, and choosing Display Port in the projector setup does not change anything. The laptop has Win 7/64, but I intend to upgrade to Win 10.

There is a FW upgrade avaliable for the projector. Should I try? It looks very complicated.

Any help will be much appeciated. The alternative is to return the laptop to Dell.

Season greeting to everybody from Denmark.

Peter