This error message comes from the MySQL database, and typically indicates that UTF-8 (Unicode) encoding is not enabled on your database.

UTF-8 is required to store non-latin characters, and the MySQL setup instructions for DeskNow mention this.

To solve the problem, you can first try and convert your existing db.

1. download http://www.desknow.com/desknow/directfiles/desknow/downloads/utf8.txt
2. open the mysql console, connect to the desknow database (u desknow), and type:
   source /var/tmp/utf8.txt
3. check that the tables have been converted to UTF-8, by typing:
   show create table MAIL_DATUM_BODY;

If the problem persists, probably UTF-8 is not supported at all in your db. In this case, you're probably still running MySQL 4.0 or 4.1 . Upgrading to 5.0.32 or later will fix the problem. (Note: MySQL 5 suffers of a related problem in versions before 5.0.32 - if you're using MySQL 5, make sure to use 5.0.32 or later)