I was using SIP correctly with my asterisk setup recently with all it's caveat but basically it worked... Same goes for my early test of video conferencing...

I recently tried to do a video conference and sip calls with a friend who just got his n800 and i couldn't hear them over SIP and video wouldn't work either. Same goes with another friend or while doing SIP with local phones. (no NAT)

Has anyone experienced this after some installation?

I'm suspecting a conflict with something i have installed since my early test, but i really don't see what software could be the cause...

Uhm, flashed to OS2007 again, then OS2008 beta...
Now in 2008 beta, video chat seems to work but SIP is randomly working, dying, ringing than dying, etc... Same goes if call from the n800 or if i call to the n800.
When/if it works it continue working through the call though.