i followed what deadmalc said and now i have msn working. This works for chinook and diablo. It's easy, just create a msn transport in your jabber account. There are many jabber servers out there (check http://www.jabberes.org/servers/ if you would like to try someone) I used jabber-hispano.org because you can configure a new jabber account from its web, and it supports avatars and you don't need to install psi, epiphany or any other stuff to do the job..
Here are the steps just in case someone else want to do it right away

1.register a new jabber account in http://jabber-hispano.org/registro/ fill the desired username and type two times the password you want
2.go to http://jabber-hispano.org/reg-transportes/ and log-in with the jabber username&pass just created
3.in msn transport fill in the username & password of your msn account.
4.Now we need to authorize all your contacts.I don't know if you can do so from the rtcomm ui. Si i used pidgin for that: add a xmpp account. for the jabber account foo@jabber-hispano.org fill in in pidgin
username: foo
domain: jabber-hispano.org
resource: tablet,home.. whatever you feel like..
password: <your passwd>
(please somebody tell us if you can authorize/add contacts from the rtcomm interface)
5.add the jabber account in your rtcomm tablet , go control panel->accounts->new->jabber.. etc

if you have several msn accounts you'll have to repeat the procedure and create another jabber account.. but remember you can use up to four different transports for each jabber account: (msn,icq,aim,yahoo)

good things:
with telepathy-haze sending your avatar didn't work, now it does.
you don't need to install the rtcomm update as long as you use OS2008 (either chinook or diablo). Rtcomm support for jabber/SIP/gtalk is included by default
bad part:
you relay on an external server to connect to msn

BTW if you find another jabber server supporting avatars, with a easy way to register/add transport from the web feel free to post which one it is