Problem with sip phones

hi there
my freepbx works when i use it with 2 softphones ,but when i use a cisco 7905g and a softphone i can call from de cisco phone to the softphone but i cant do it from de softphone to the cisco i get message from x-lite saying that “call failled : service unavaiable”



Do you use Asterisk or Freeswitch ?
Can you paste your log file when you try to call the Cisco phone from the softphone ?

Thank you.