SIP Console Message

Since installing the latest version of Asterisk via SVN (1.2 Branch) i am getting a strange message appearing in my Asterisk Console. The message is :-

"Got SIP Response 481 “Call Leg/Transaction Does Not Exist” back from 192.168.32.4

Can anyone help with what this means?? It doesnt seem to be generating any errors with the system that I can see.

Thanks