The workaround is to set environment variable
DYLD_LIBRARY_PATH to be
/opt/X11/lib/flat_namespace
This is best done in the login script for your shell. If you use tcsh (as I do), that file is
.cshrc in your home directory, and you would add the command
setenv DYLD_LIBRARY_PATH /opt/X11/lib/flat_namespace
to that file. By itself, this will have no effect -- until you start a new shell (command window). To make it work in the shell you are using NOW NOW NOW, you can just manually execute the command (e.g., copy+paste into the shell).