Messages beta hangs. How to remove it or at least its accounts? I've received a huge iMessage and now the App hangs. I can't remove the App, because it's only possible via the menu item which is not responding. Removing ~/Documents/iChat/* and ~/Library/Messages/* didn't help either.

Any ideas of how to remove it or at least its accounts?
Messages always hang on my Mac as well, error telling me no account set up etc, and restarting my Mac always helps to bring it back to normal.