It would be wise if you can check the system requirements of matrox triplehead2go with the original equipment manufacturer and see whether if you have all the required features in your system. Such errors are mostly because of the configuration of system.
Do you understand how this works. You send triple wide video 1920(3x640)x480 and th2go will split this into 3 monitors 640x480 each. If you send just 640x480 you get just the middle monitor showing the video bacause you do not have any content on the side monitors.