If you see an error like the one below in your Cisco ASA log files, check with the other end and make sure your transform-set matches.

QM FSM error (P2 struct &0xd7fed708, mess id 0xcc86fb64)!

The QM FSM error message usually relates to a configuration mismatch. Although checking the crypto ACLs is often the first course of action, it's easy to forget the transform-set.