Rhino to D5 Render Converter - Material Issue

When I try to open the D5 Render file directly from Rhino all the materials that I previously applied in D5 are reset to the white default material. But when I open the file directly from D5 Render all the materials that I applied are correctly displayed. Why is this happening? Now I need to change some things from my rhino model but I can’t because I don’t want to loose all my previous work.