What does the error 'cannot find tokenRefBangTrack.st' mean?

You have probably mixed tree construction operators (like '!') and the new rewrite syntax in a rule.

E.g. this rule will provoke the message:

: ID ( COMMA! ID )* -> ID+

Thou shalt not mix rewrite syntax and tree construction operators. Admittedly ANTLR should print out a nicer error message for this.