Materials in Explorer show inconsistently

Materials in Explorer (Win 7 x64) in Revit ArRevit_MG01rv show except the Plastic transparent yellow and blue. Most will show in Autocad arnxt64_0329 after being viewed first thru the Revit material viewer. If there were some way to retain the large icon view settings in Explorer, that would be a help, but I haven't located such a method so far. I've no idea why the AutoCad version won't show except thru the Revit version first.