A disaster. Mail keeps crashing in Snow Leopard. First the spinning wheel comes, then it crashes. When I try to restart, it says "Mail canceling restart..." Spinning wheel also in menu bar. It doesn't respond. Go to System Preferences and it freezes after showing spinning ball.
As soon as Mail 4.0 is trying to open my different folder, the colour wheel is turning a few second, and then the application crashes.
I have tried to restart the Mac with Mail 3.6 but with an error message 'Your OS cannot open a previous version of Mail (3.6).'