gistfile1.txt

(defmacro defrecord [rec args]
  `(do (clojure.core/defrecord ~rec ~args
    'clojure.lang.IFn
    (list 'invoke '[this] 'this)
    (list 'invoke '[this n] '(repeat n this))    
    (list 'applyTo '[this args] (list 'clojure.lang.AFn/applyToHelper 'this 'args)))
       (def ~(symbol (str "new" rec)) ~(symbol (str "map->" rec)))))

ClassCastException clojure.lang.Cons cannot be cast to clojure.lang.Symbol

you already have a syntax-quote on line 2, so you don't need to do any more quoting. However you should use the gensym (trailing #) for safety purposes. Otherwise it's possible for the macro to be invoked somewhere where the symbols this,n, or args might refer to something else. In this case it should be fine either way, but that's the usual practice.

this is untested by the way:

(defmacro defrecord [rec args]
  `(do (clojure.core/defrecord ~rec ~args clojure.lang.IFn
         (invoke [this#] this#)
         (invoke [this# n#] (repeat n# this#))
         (applyTo [this# args#] (clojure.lang.AFn/applyToHelper this# args#))
       (def ~(symbol (str "new" rec)) ~(symbol (str "map->" rec)))))