[Serusers] SER service: registration problem (load balancing quirk?)

Dear SER users, I'm experiencing occasional problems with my SIP clients registration to the (free) iptel.org SER service. I'm not sure if this is the place to ask questions regarding this service. If not, please give me a pointer who/what I should contact. I've made 2 tcpdumps. 1 from a failing registration request and from a successful registration request. The setup for both situations is the same. These captures were made within 40 minutes from each other. In both cases the first registration attempt is replied with a 401 Unauthorized (obviously) which request for authentication. In both cases my SIP client (SJPhone) replies correctly (I assume) with a new registration and the requested account credentials. In the case of a successful registration the SER replies with a 200 OK. In the case of a failing registration my SIP client receives another 401 Unauthorized message. What struck me is that this second 401 is sent from another SER system. (The "Server:" header from the first registration attempt is different from the second registration attempt.) The first header has "Server: Sip EXpress router (2.1.0-dev16-tcp (i386/linux))" while the second 401 has "Server: Sip EXpress router (2.0.0-rc5 (i386/linux))". (note the difference in SER versions) I've verified that in the case of a successful registration the Server header in the first (401) and second (200) response are the same: "Server: Sip EXpress router (2.1.0-dev16-tcp (i386/linux))" Is this some kind of weird load balancing quirk? From a security point of view I don't want to send my TCP Dumps (with my authentication) to the mailing list, but I can send it to a personal email address when required. Thanks, Tom