Problem if you have more than 9 servers
Problem if you have more than 9 servers or if you join the same server often so the server_id continues to rise..
When it has reached 10, then the installer will try to create MySQL user with username "ispconfigserver10".
But that's 17 letters, MySQL only allows 16 letters in username, this could be fixed very quick by editing the "installer_base.lib.php" in the folder ispconfig3_install/lib/.
On line number 233, char 47. "ispconfigserver" change that to "ispconfigserv" and the MySQL database will not complain about username length.
I doubt anyone will have more than 999 servers :D
Thanks! Bergur in Iceland