#880 Drag date misbehavior

[Greg]

1) Using middle mouse button, drag a single task on Gantt chart. If this task has successors, other tasks can jump around. These tasks can be parents, children or completely unrelated ones. Adjusting the date manually does not cause this, only dragging task around with middle mouse.
2) Select multiple tasks then use middle mouse button to drag the tasks to a different date. Tasks move BUT the gantt chart is not frozen. The rest of the app seems to work, menus, context menus, but the gantt chart is now frozen until new project loaded.

System:
MS Windows 7 64bit
GanttProject v2.0.10