resolution via DVI lower then via VGA

Hello,

I need your support for my new HW composition.

I have a new DELL Latitude E5440 and the fitting DockingStation DELL PR02X.

Connecting my monitor via DVI I get a max. resolution of 1440x900.

Connecting my monitor via VGA I get a max. resolution of 1680x1050 (max of monitor).

With my former laptop of FSC I could use the monitor via VGA in the highest resolution.

Can you please help me to get the high resolution via DVI?

Thank you very much for your help in advance,

Scorino