Encoding Problem

Hi.

I'm receiving this error message:

invalid UTF-8 byte sequence detected

SET search_path TO administracao,public;

CREATE OR REPLACE FUNCTION inserirTela(text,text,text) RETURNS text AS '
DECLARE
sName ALIAS FOR $1;
sDesc ALIAS FOR $2;
cSist ALIAS FOR $3;
BEGIN
SET search_path TO administracao,public;

INSERT INTO telas (nome_tela,descricao,sistema) VALUES( sName, sDesc, cSist );
RETURN ''Registro inserido com sucesso'';
EXCEPTION
WHEN unique_violation THEN RETURN ''Ja existe uma tela com este nome'';
WHEN others THEN RETURN ''Erro ao inserir registro'';
END;
' LANGUAGE plpgsql;

The problem is in the RETURN messages... if it's oculted the error not occur.

What i do?

My database is UTF-8.

Thanks.