http://www.frictionalgames.com/forum/thread-20345.html This thread is more accurate :] The old one probably has some errors in execution (which the new one most likely also has)!
To answer your question. Let's say you make a wall. The wall has one texture (image) called "MyWall.dds" where the color information is stored. In order for modelview to create your .mat file the material (of your model) in Maya has to have "MyWall.dds" assigned to the color slot. "MyWall.dds" should also be placed within the folder of the .dae (the exported model).
In case something has gone wrong, delete everything except the .dae and the .dds.
Edit: Also make sure you have triangulated the model. "Mesh --> Triangulate" while having it selected (in maya).