Perhaps a common issue. Trying to build a tunnel from our Cisco 3030 to a Watchguard Firebox X20 Edge. No matter which side initiates the tunnel, phase 1 completes. But if the Watchguard side tries to bring up the tunnel, phase 2 fails and neither side can ping the other. The errors on the 3030 are "All IPSec SA proposals found unacceptable!" and "QM FSM error". If we send traffic to bring up the tunnel, we get the same errors, but also get a phase 2 complete and we're able to successfully ping a device on the customer's network. Have verified phase 2 settings are the same. Firebox uses 3DES-CBC for Auth, only difference I can see.
I have this problem too.