On the difference between [nitaienai1] and [nitaienai2] There are two たえないs of note in the Japanese language... hurray. How to distinguish them? [nitaienai1] is for saying you just can't stand something and should be constructed from VERB辞書形 + にたえない [nitaienai2] is for saying that you have a strong emotional reaction to something - "氏の当会へのご援助はまことに感謝に堪えません｜We cannot be too grateful to him for the help he has given our society." and should be constructed NOUN + たえない.
Both are on the old JLPT 1 syllabus, if anyone knows what's on the new N1, please advise