This error message means that DL_POLY_2 has been unable to find all the
atoms described in the exclusion list within the simulation cell. This
should never occur, if it does it means a serious bookkeeping error has
occured. The probable cause is corruption of the code somehow.
Action:
If you feel you can tackle it - good luck! Otherwise we recommend you
get in touch with the program authors. Keep all relevant data files to
help them find the problem.