Does your color image open in fcheck? What about the size of your motion images? If there is actually motion vector data, the files should be quite large. Are your motion and color images the same size and have similar file naming style (same padding etc...)?

I'm only guessing here. Maybe you should post one frame of the files for testing. I cannot help much further since I don't currently have access to a computer with Maya. I'm in a process of relocating so I might not be around in a while either...