This paper presents examples from case studies of two groups of teachers learning to use a synchronous text-based virtual environment. When teachers learn to use a new system for their professional development, at least three matters must be learnt simultaneously: the system itself and its commands, how to relate to other participants in the learning experience and the content that is focused on the discussion at stake. From the analysis of on-line sessions, we found the following difficulties: 1) Confusion about visibility, 2) Multiple threads, 3) Interruptions 4) Repeated requests for attention from learners and from leaders. We relate these difficulties to the need of “orchestrating ongoing activities” in synchronous environments. We show how difficult it is to produce adequate messages (communicate), take account of others' actions and messages (collaborate), and manage their own activity through a Moo-mediated environment (learn).