Cannot recognize Greek characters

Guys, i have problem with uddeIM as it cannot recognize greek characters (even though i think i have never set it in greek). Please see the image attached in order to understand what do the users see when they try to send a message.

Can anyone help with this?

Thank you.

Please enable UTF-8 in uddeIM backend (system tab). This should fix your problem.

I tried to do that, but i get the following error (see pic please).

Please read the FAQ according the FTP mode. Your access rights are not correct, so uddeIM has no access to its configuration file.

I changed the permissions of the /config.class.php to 766 but it still didn't work so i manually changed the php file to UTF-8. Now in the configuration in the backend i can see that it's UTF-8, but the problem has not been solved. I get the same characters.

Can you also tell me what does this mean so i can search for it in the FAQ file:
JFTP: :write: Unable to use passive mode

Any specific suggestions please?

OK fixed it. But i guess every time i want to change something i will have to disable the ftp from global configuration.