VMS Help UIL, Compile Time Errors, UNKNOWN_CHARSET  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  ERROR:  The message is pointing to a context where a  character  set
  name  is  required.   You have not specified the name of a character
  set in that context.

  USER ACTION:  Check  for  misspelling.   A  list  of  the  supported
  character  sets  is  given  in  the  "VMS  DECwindows User Interface
  Language Reference Manual".  If you specified  case-sensitive  names
  in  the  module,  check  that the character set name is in lowercase
  characters.