This causes an error with users that have spaces in their usernames.
To fix....
In chatroom.php need to find
$Username = $user['U_Username'];
and add below...
$ircnick = str_replace(' ','_',$Username);
And in chat.tmpl
Find
<param name="nickname" value="$Username" />
Replace with
<param name="nickname" value="$ircnick" />