Sounds like you need to setup your MySQL users for each host you plan to chat from.
GRANT ALL PRIVILEGES ON databasename.* TO 'username'@'hostname'
IDENTIFIED BY 'secret' WITH GRANT OPTION;
Of course, this is not exact and you will want to change the GRANT permissions to fit your needs. The above script effectively gives you full persmissions (admin rights) on the database you assign it.
The *hostname* field can be interpreted as the "client" host name -- basically any host that will be accessing the MySQL database.
See the MySQL Documentation:
Also make sure the firewall isn't preventing you from reaching it also.