This answer was posted elsewhere a few days after leaving my question here, so I’ll share it for the benefit of others plagued by this problem. ———————————- In Project Server 2010, when a Timesheet is created, it links each timesheet line to a Project Plan Task using the Task’s UID. If you move that Task’s location in the Project Plan by dragging it, you’ll be OK. If you “move” that Task using Cut and Paste, you’ll delete the old Task and create a new Task, with a new UID, breaking the link to the Timesheet! As long as no Actual Work has been done, that’s not an issue; once Actual Work has been logged, you can be in trouble. To be safe,avoid using Cut and Paste with Tasks in Project Professional.