[Serusers] Error message I don't understand

Hello, I'm trying to use the presence agent that is in the CVS version. I added the module and the lines ---- if (method=="SUBSCRIBE") { subscribe("registrar"); break; }; ---- to my ser.cfg file. By changing this I get the following error message when trying to "sign in" with the msn messenger UA: ---- 15(23129) ERROR: t_reply: cannot send a t_reply to a message for which no T-state has been established 15(23129) send_reply(): Error while sending 200 OK ---- What does this mean? I admit I don't know a lot about the details of the SIP protocol, but if you'd give me a hint on where to search, it'd help me a lot. Is the presence agent in CVS already usable at all? If yes, could someone please provide me a working config file? Thanks in advance, Stefan Schmidt