Online consultant on your server

Good day, there is a service in which you want to implement online consultant. That is to allow the user to ask questions directly from your browser.
There are team managers(until the 2nd). Messages should be sent to one of the managers and further conversation would only go with this Manager.
It is desirable that if the user after a while came to another Manager, this Manager could see the history.
And it would be quite wonderful if messages came in jabber/icq/etc.
And most importantly the requirement that all of the magic you worked on our server, because paranoia.
I would like to put the whole thing with minimal fuss.
Thanks in advance.
UPD
Current candidates:

• www.helpcenterlive.com/
• www.craftysyntax.com/index.php
• mibew.org/ru/ (While favoured him, looking code)

UPD2
Stopped at mibew.org/ru/. Thank you all.