So, I made a new project and reimported the assets, nothing is helping. Yep, one material is assigned. I noticed something weird in the output though. Why is the "model" loading for the parts I've made but not for the mods I've obtained from other authors? All others show Load(Texture)... Also I came across another forum post saying something about a .mu file being incomplete/corrupt if its very small, under 10k. I took a look at my model and it's 1-4k depending on the order of steps I use in Unity (which is really weird). What a pain in the ass! Lol, and I agree, Modo is awesome. Way more efficient coming from Max.
Edit: I figured I'd add in my model and texture, could you run it through your unity and see how it goes? It doesn't have a collision mesh as I've been just adding a mesh collider to the main model, its so low poly I just doubled the count with a collision mesh, which seemed excessive. The original mesh I used had a seperate collision mesh and still got the error so I figured there was no harm in removing it.
https://drive.google.com/open?id=0B2imY9mkpx_5LU5Wc2dUd3RRTGc