[Serusers] Mediaproxy Error

Hello. The other day I asked about video speed in sessions. Now I have seen that although I can establish video sessions between UAs, I get this error: "error mediaproxy/getSDPMessage(): SDP message has zero length. use_media_proxy();failed to get the SDP message" I mean, we can see and hear each other ( with really really bad video ) but I have these errors. I have seen with ethereal that the INVITE packets carry an SDP packet too, so I don't understand why mediaproxy can not extract SDP packet. Maybe this is why video quality is so bad ? Does anyone know why this is happening ? Thanks in advance: Kiko