If some symbols, such as \Box and \lhd, no longer appear to
exist, then your system administrator has probably upgraded your
version of LaTeX to either
NFSS or LaTeX2e.
In the former case, use
oldlfont.sty (see problems with \rm, etc.).
In the latter, use the package latexsym, which is part of the
LaTeX2e distribution, or the package amsfonts, if
it is available.