[Serusers] ser+sems t_write_unix error !

[iptel]

I have:
Sems downloaded from: http://www.iptel.org/drupal/sems
Ser version: 0.9.6 

in ser.cfg:
unix_sock="/tmp/ser_sock"
sock_mode=0666
fifo_db_url="mysql://ser:user@server/ser"
fifo_mode=0666
........
if(!t_write_unix("/tmp/sems_sock","conference")) ....
... 

in sems.cfg:
socket_name=/tmp/sems_sock
reply_socket_name=/tmp/sems_rsp_sock
ser_socket_name=/tmp/ser_sock 

When i call conference, this error appear on screen: 

t_get_trans_ident: no transaction found
assemble_msg: t_get_trans_ident failed
ERROR:tm:t_write_unix: Error in assemble_msg
ERROR: t_reply: cannot send a t_reply to a message for which no T-state has 
been established 


Please, Can anyone help me?!!!!???
My operating system is Linux Fedora core 5 !
Thanks