[Serusers] RTP proxy and Cisco IP phones

Hello to all, Im having huge problems connecting Cisco IP phones (7940 and 7960) to my SER. I m using the 7.5 SIP firmware. Before that, all phones (softphones, hardphones,...) worked, but the Ciscos seem to have problems to register and to make calls. The bigger problems are in the RTPproxy part of my ser.cfg.... the Cisco IP phones cant get out of this: if (method=="REGISTER" && nat_uac_test("3")) { fix_nated_contact(); log(1, "LOG: ciscos doesnt work with NAThelper \n"); force_rport(); setflag(2); }; The phones dont register with SER when I have "force_rport". The phones cant make calls between them if I have "fix_nated_contact" and "force_rport" If someone could manage to put Cisco IP phones to work with RTPproxy and NAT helper, please give me a hand. Thanks Joao Pereira www.fccn.pt