Whenever there is a spac after an open parenthesis, one gets a TK error. For instance, try and type the following definition:
(defvar xxx '( abc x y z ))
Leave a space between the open parenthesis and abc. The Tk message is:
Index 0 out of bounds for (SIMPLE-ARRAY CHARACTER(0)), should be nonnegative and <0.
I guess the problem has to do with the token coloring algorithm.