same here, asteroids aren't rendering, replacing with the player ship model makes it work, leading me to believe that it's something to do with the mesh file itself...also collision is not working for me either.

Hmm, my asteroids aren't visible when I run the completed project, I must have made a typo somewhere.

I don't get it, in my computer the example runs just fine. Could you create an issue with your problem and the stacktrace?

A NullReferenceException pops in Asteroid.cs, at the CollisionMove = newConvexHullCollisionMove line: Object reference not set to an instance of an object, whenever I hit 'A' to create an asteroid.
I've also copy/pasted straight from your own code, as well as ran the original unmodified source code. The error appears every time.

Thanks for making such an awesome step-by-step tutorial! I'm gonna try it for WP7 and see how smoothly it will run.