Hi peterleinchen and supergaban, thank you for your quick replies.

Audio calls are working now indeed after flipping the switch to REGISTER underneath the Keep Alive Mechanism.

Video calls don't work yet though. Whether started from tablet, laptop or n900, the video window opens for a second and then closes again.

Any suggestions?

Edit: changing the video codecs on linphone on laptop worked. The standard was VP8 which did not work on N900 apparently.
Now I need to find a way to use MP4 / h264 codecs on linphone's ipad app without jailbreaking...it says 'compile from source' if there is anyone who knows how to, or know of a good audio/video SIP client for iOS, then I can really start using it (I will be mostly contacting someone on an apple device)

In any case, very happy that SIP with audio is already working on my N900. But video...would make me ecstatic