Force Quitting Mail on Shutdown

Hi
Ever since I have bought my retina MacBook Pro about 4 out of 5 times I have to force quit mail when shutting down. This problem has happened on Lion and when I upgraded to Mountain Lion (10.8.2) and I have no idea how to fix it.
Does anyone know how to fix this?
Thanks

This is a possible fix.

First, copy all the mails on the Mailboxes --> Inbox to any folder on your Mac.
For example, all the mails from the account .Mac goes into a folder named 'Mac account'.

The next steps are :

1) copy the Mail folder /Users/username/Library/Mail to the folder you created.
2) close mail app
3) From de mail folder inside Library delete all the content.
4) Open Mail app. (only the emails will disappear, not the accouts.)
5) Import all the mail you placed in 'Mac account' folder again.

Please post back if this helped you.

SM

Thanks for the idea but it didn't work. I was still having to force quit mail. While I was in Manchester I popped into the Apple shop and asked them and they said the best idea was to reinstall Mountain Lion. I have now reinstalled it and it works perfectly.
Thanks for your help anyway.

It does happen upgrades can be a bit buggy. Always best to download OS, burn to a USB thumb drive, backup and do a clean install.