Hmm that's weird..
I've been experimenting a lot lately with objects being added, and seeing as how your star trek model is so highly detailed, I might give that a go
Saw that somewhere, forgot where it was..can you link me please?
Well, if you cant get any colours going, try texturing INSIDE Terragen. I found that is helpful sometimes, however, your conversions should work...maybe you forgot to link to the mtl file?
Here's one render where I used a population and textured mainly in Terragen: