I found the problem, and it was me: my original entry does not have a "TODO" in the title. (My reasoning for not putting the TODO was that it's a project, so as such it should not appear in my agenda, only the tasks should appear.) So when I close it (change the state to DONE), the "choose a state window" remains open, which I hadn't noticed before. When I choose a state in this window, then the project becomes scheduled again.
To reproduce: * Project SCHEDULED: <2012-09-02 Sun +1m> ** TODO task1 ** TODO task2 Changing the project status to DONE leaves the "choose a status" window open. I guess I'm too much into an OmniFocus way of organizing thing, and need to dig deeper in orgmode to find the canonical way of doing this. For repeating projects, do you use checklists like Memnon Anon? Best, Alan