I searched all the threads on this topic, and couldn't find anything exactly the same... I haven't installed any plug ins, altered the accounts, or done anything different in mail today. For some reason, it all of the sudden stopped opening - can't even get a main screen up when I launch it. I've tried deleting plists, holding shift on start up, checked for any problematic mail being downloaded via my iPad, repaired permissions and even tried to launch yesterday's version from Time machine. I've tried opening Mail without being on the internet too. I have an exchange account and a mobile me account on there, and both have been working perfectly until today. I have a 2009 Unibody Macbook Pro running 10.6.4. My crash report is almost twice the length of the allowed word count so can't post it - is there a specific section I should cut and paste that will help? Thanks.