OK, after some investigations here are my findings. I post them here so if some one get the same error he might get hints. It seems if the the other end of the call has his soft phone closed, this error is returned. I tried to increase the max size to 4096 and now I get the "Too many hops" error. Which means, the message is forwarded way too much time, beeing increased over the 2048 limit. Now, why do I get a route loop when a user is offline...I suspect this "...if (uri==myself) {..." of beeing the culprit. I added various alias to the proxy ip adress, to the proxy name and even the domain name bu nothing worked out. Any ideas ?