My first thought is that your ground textures have gone awol, or possibly the xml file that references them. Check carefully in the assets route descriptor that the files exist and that all the texture files are there.
Seriously, it looks like some files have disappeared during a Steam update. A Verify Cache via Steam will probably put everything back where it should be. See the FAQ area for details on Verify Cache.
Mike
Mike in OZ - Author of TS-Tools & Route-Riter. http://www.agenetools.com
I'm not arguing (just explaining why I'm right).
Before we go for any of the more complex solutions, start with the simple process of clearing the blueprint cache. It may be worth manually searching for any blueprints.pak files and deleting them