"Unknown server response." when server returns 500

[du-song]

13:23:14: (Libpurple: fetion)

received - Wed Nov 25 13:23:14 2009

SIP-C/2.0 500 Server Internal Error F: 569659056 I: 1 Q: 20 R

13:23:14: (Libpurple: fetion) in process response response: 500 13:23:14: (Libpurple: fetion) in process register response response: 500 13:23:14: (Libpurple: fetion) Unrecognized return code for REGISTER.500 13:23:14: (Libpurple: fetion) fetion_input_cb: read error