[pjp]

Sounds like you have automatic layout turned on. You may have turned it on accidentally, or by choosing a document template that has it on by default. (Templates in the Brainstorming and Organizational Charts section of the Template Chooser have automatic layout turned on, the remainder do not.)

To turn off auto-layout, go to the Canvas : Diagram Layout inspector and uncheck the "Automatic layout" checkbox. Does that help?