Mail.app crashing at launch. Help, please?

I would run disc utility and fix permissions then reboot

First I would try starting up Mail while holding down the shift key. That will make it so Mail starts without a mailbox selected.

If that doesn’t work try removing the preference file for mail. Don’t delete it, just move it someplace else. Do this while Mail is closed.

It is in /Users/YOURUSERNAME/Library/Preferences/

The file you want to move is com.apple.mail.plist

Try starting up mail again. You will need to create your account again but your mailbox should be intact after you enter your info.

I ran a permissions repair to no positive result.

After holding shift while starting Mail, the app came up without a hitch. Thanks.

I have no idea why starting without selecting a mailbox would have an effect…
any enlightenment there?

This might explain it.