Leopard Mail unexpect quit

Today my Leopard Mail quits unexpectedly, so I can’t even start my mail. I don’t think I did something to Mail App at all, it just happened to quit. I start to think may be this is something that MobileMe and Google Mail have something todo with it since I have only these two settings in my Mail App. Thus, I have to start all over by delete com.apple.mail.plist from ~/Library/Preference and start Mail App again. However, I have to setup all the account all over again.