I got en error on messages configuration tab. I can't change anything.
I recently add a table into the message for "User email body (offline payment) " and since I do it! I'm not able to change something into configuration anymore.
It must be something wrong with your site. Change that setting doesn't make the configuration doesn't work anymore. Please submit a support ticket giving me administrator and FTP account of your site. I will check it and tell you what is wrong !