The Scene: I have created a fancy Teapot and applied multiple Arch & Design materials to it. Imported models will usually generate a similar material structure.
The Problem: 3DS Max defaults to Mental Ray Arch & Design materials when you import a model. This material type is (mostly) not supported by IW. I say mostly because Infraworks will respect the material color, but won't recognize if there is a bitmap image associated with it. I export to .dae and this is what I see in IW. You can see Infraworks respects the colors, not the bitmaps. To resolve this, we need to convert the materials to standard.
The Solution:
First: DOWNLOAD THIS SCRIPT
Second: Drag and drop it into the 3DS Max scene like this:
Third: There is no third, you're done!
Check out your materials (press m) now. Standard, just like we like it!
Export this to DAE and you will see accurate results in Infraworks!
Good luck!
Great script! I noticed that it creates a lot of duplicated materials, so I merged your code with a script I had that uses a different technique to replace the materials: