Consider the following scenario:
A Microsoft Office Communicator 2007 R2 user joins a Lync 2010 conference as an attendee from a join link.
The Office Communicator 2007 R2 user tries to start sharing.
In this scenario, the Office Communicator 2007 R2 user cannot start sharing, and receives a rejoin link. Additionally, the user receives the following error message when the user clicks the rejoin link:
Cannot rejoin the sharing session because the sharer has left.
To work around this issue, the Lync 2010 conference organizer can make the Office Communicator 2007 R2 attendee a presenter. To do this, right-click the attendee and then click Make a Presenter.