CAD tip # 8597:

There are three possible sources of this problem:

1. Graphics card - Showcase uses a lot of graphics power, any incompatibilities may cause display problems; check and update your gr.card Windows driver
2. Non-unified normals - some faces are imported as back-faces (reverse), facing away from camera; you need to unify faces to "look" at camera - use Edit > Always Face Surface Normals to Camera in Showcase
3. Overlapping faces - rounding errors can make overlapping faces "flash"; two different surfaces at the same geometric location (e.g. terrain and asphalt road) may display as alternating faces depending on your current view vector; there is no easy fix for this - try to slightly elevate the "upper" surface in Z-axis