Shoutbox

I'm try to develope a new script plugin.
In OnEvent_ChatWndReceiveMessage
i wrote:
...
var txt = "New msg:\r\n" + sMessage.substr(5);
Debug.Trace(txt);
return (txt);

in Debug window i can see the correct text but on message window i get a truncate text
This happens when the msg is short than 6 chars.
'return sMessage' returns the correct message


Is a bug or i wrong something?