jamflyer- I am surprised to hear that. You are right-- i have changed ff tickets among all NY airports, on AA and other airlines, with no charge. And I also did it about 6 weeks ago.
Did you inquire if there was a policy change? Is it possible that the agent you were speaking to was making a mistake? It would be $100 to change any other ticket, but not a ff ticket. That has always been my understanding.
------------------
Amy Wilson