Has anyone had problems with virtual parts disappearing?  I had an assembly bulit using some virtual parts.  The assembly then went unused for several weeks.  When it was reopened the virtual parts were missing.  In the featuremanager the parts were still listed as virtual parts (i.e. bracketd name).  However when I attempted to open the file it told me the file could not be found in a temp directory on my hard drive.  The only way I could fix this problem was to re-create the files.  Also I am not the only user that has had this happen.  If there is any help out there it would be appreciated.