I doon't have a solution, but I had a diiferent wierd mail behavior. I tried to reply to a message with command-r, and nothing happened. I hit it again and nothing. Finally, I pressed the icon in the toolbar and again nothing. I closed and restarted mail and there were my three reply attempts.
This is a late response but just in case there are other people having this same problem and searching for a solution on MacRumors, we thought we would give it a shot.
We've had customers contact us with this same problem so we posted our response on the PowerMax resources page. For troubleshooting ideas, you can view our post: Safari and iChat Quitting Unexpectedly.