Getting Error Message in Asterisk CLI Prompt

Hi,

I am having asterisk 1.2.7.1 with TDM2400. It was configured with 75 extensions approximately. In Asterisk CLI prompt, I am getting this error message like

Got SIP response 481 “Call/Transaction Does Not Exist” back from 125.21.164.249
Got SIP response 481 “Call/Transaction Does Not Exist” back from 125.21.164.249
Got SIP response 481 “Call/Transaction Does Not Exist” back from 125.21.164.249
Got SIP response 481 “Call/Transaction Does Not Exist” back from 125.21.164.249
Got SIP response 481 “Call/Transaction Does Not Exist” back from 125.21.164.249
Got SIP response 481 “Call/Transaction Does Not Exist” back from 125.21.164.249
Got SIP response 481 “Call/Transaction Does Not Exist” back from 125.21.164.249

very frequently. So, Please help me to solve this problem. I would appriciate your eralier response.

Thanks
Krishna Kumar,
System Administrator