I have had some issues with build B85 ADC GM when copying my Users folder back over (using ditto). Both Mail.app and iChat have gone south on two installs after a couple days. My suggestion, and it is also what I am going to do now, is to do a clean install and import mailboxes and other application prefs on their own, and one by one. In my case, it very well might be preferences from third party apps and haxies I had installed in 10.2 that just don't play well under 10.3.