I have an assembly of several components. When I click on the main part (the first one I inserted into the assembly) and click on the "Open Part" folder icon, the part appears briefly on screen and then vanishes. When I go back to the assembly, it is not visible there. In both the files the part and its features are still visible in the Feature Manager design tree. If I close those windows and try opening the part directly from its file, the screen just comes up blank. Does anyone know how to fix this?