Before this drives me mad, anyone offer an opinion as to why, when trying to install a tunnel through a mountain, some of the tunnels have terrain inside them, and others, which don't, cause surveyor to crash.  Using TS2010 here, and 5m grid, which gives nicer shaped scenery in mountains.  I've tried numerous of the tunnels available, and invariably the ones with no scenery inside are crashing it.  I even levelled the mountain off at the tunnel height, and built it across flat terrain on the surface, and it still crashed.  The stupid thing is I already have a tunnel on the map, which worked fine, although that was put there with a 10m grid, and upgraded to 5m.  The tunnel is level, straight, at height 69. 
There are no errors showing in content manager for the route, and when I had a tunnel with scenery showing inside, I could drive through it.
				
			There are no errors showing in content manager for the route, and when I had a tunnel with scenery showing inside, I could drive through it.