Disappearing Terrain

This is my route I'm building in TS2010. Note in the first pic, all the terrain is there (untextured, obviously.) In the after pic, all that's left is a blank baseboard. Any ideas?


Before



After

I basically lost about 8-10 hours work since this terrain disappeared while working on another part of the route.

I just experienced this while looking at a route in Surveyor, but it resolved itself after a couple of minutes, are you certain it's "gone" for good?

Yep, unfortunately. I even tried importing it into another installation; all gone. Mind you, it's not just a few sections that disappear temporarily from view either, but a whole section with all Transdem-formed terrain.

You probably have checked this already, but just to be sure:
Did you check if you used different sessions for this route or maybe switched a session to 'dont show'?
Maybe the content is still there but either just hidden or in a different session.