Well, I renamed the 'newlisp.vim' file to 'lisp.vim' and indeed, now it's ok.
This seems to be the only way then? While if I state ":set syntax=newlisp" with the old file name newlisp.vim, then the ecalamation marks are not highlighted (e.g. '!' and '!='). Also changes in 'filetype.vim' did not change this situation. Maybe the original 'lisp.vim' is conflicting with 'newlisp.vim'?
But anyway, it works now, thanx.