Help with Trainz error?

[engineerboy6561]

So I've gotten back into station modeling and rendering, and am trying to get some of my station models into Trainz. Currently, I've found a plugin called RubyTMix that lets you convert Sketchup files into most of the pieces needed for an asset; you put in your .skp file and you get back out a .im file, a bunch of resized, reformatted textures, a thumbnail, and a config file. I was able to use Content Creator Plus to assemble an asset with those files, but when I try to load it into Trainz the program claims to be unable to load the mesh or the thumbnail and the asset is unusable. Thoughts on how to fix this?