QA. Look into it. Then perhaps you’ll learn about things like “iTunes 10.6 can’t see my iPhone 4S” before you release. There’s not a lot I can do about usbmuxd core-dumping.

The key error seems to be when you start up the new iTunes:

3/7/12 4:34:18 PM	iTunes[10876]	_SubscribeForMuxNotifications (thread 0xb081b000): USBMuxListenerCreate: Connection refused

[Update: you have to reboot your machine to get it to work. Nice.]