It looks as though RailClone's adaptive display mode has activated. This happens when the face count for the objects exceeds an adjustable threshold. The original geometry is replaced by boxes in the viewports to ensure that they remain fast and responsive. This is purely a viewport effect though, and the style should still render correctly.
You can deactivate this by changing the Viewport
mode to Mesh
using the settings found in the Display
rollout. But for large areas with many millions of polygons you may get some slow down. More information about this can be found in our online documentation here
I hope that helps.