To be honest, i have not tested multi-party I'm going to assume your using R2. I'm also not sure if the MOC client support multi-party video anymore as i think they are trying to get people to use Live Meeting instead. i could be wrong.
Not sure Tandberg device? is this similar to a Polycom CX700? and runs a slimed version of Windows CE + Communicator Phone Edition... If your running the original beta firmware i don't believe the R2 version will allow updates at all (you have to make sure there patched to the latest R1 update), which is just ridiculously stupid. oh and you cannot manually