[Serusers] problem with 481

Serusers， SER server starts and registration is successfull,but msn client cann't communication each other .when I use Ethereal: ........ 　　 Request:INVITE sip:test@192.168.0.206,with session description Status: 100 trying --your call is important to us Request:INVITE sip:test@192.168.0.207:10328;with session description Status: 100 trying Status: 200 OK,with session description 　 Request: BYE sip:test@192.168.0.206;ftag=f92d17003fg64albad12e56a04c4c5aa;Ir=on Status: 200 OK,with session description Resquest:ACK sip:test@192.168.0.206;ftag=f92d17003fg64albad12e56a04c4c5aa;Ir=on Resquest:Message test(a)192.168.0.206;ftag=f92d17003fg64albad12e56a04c4c5aa;Ir=on with session description Resquest: BYE sip:192.168.0.208:13698 Status: 200 OK Resquest:ACK sip:192.168.0.208:13698 Resquest:Message sip:19292.168.0.207:10328. with session description Status: 200 OK Status: 481 call leg/transaction Does Not Exist Status: 481 call leg/transaction Does Not Exist ..... I donn't know how to do? please help me!Thanks! 　　　　　　　　zhangsezhen(a)sict.ac.cn 　　　　　　　　　　2004-07-13