Hi Mike,
I know you are Python-literate -- I found this in "NatureTerrainGenerator.py":
TEMPLATE_PROP_PATH = os.path.join(RLPy.RApplication.GetTemplateDataPath(), 'iClone Template', 'Props', 'Nature Terrain Generator')
TEMPLATE_MTL_PATH = os.path.join(RLPy.RApplication.GetTemplateDataPath(), 'iClone Template', 'Materials Lib', 'Nature Terrain Generator')
Is your content still in these directories, or did it get moved somehow?