I really need to know more about your setup. Are you using some automation to code to automatically generate a diagram based on an Access database? If so, where are the original shapes?
I would like to clarify some terms so that we are speaking the same language. The stencil is the green container window that stores Master Shapes. Master shapes are the shapes in the stencil, and they are basically read-only, reusable objects. From these masters you can make copies (referred to as instances) and place them on your page. The "icon" is simply the 16X16 or 32X32 pixel symbol used to represent the master shape inside the stencil. If you right-clicked the Master shape in the stencil and choose Edit Icon from the menu, then you would not be editing the actual master shape. Rather, you would be editing the primitive "icon" in the stencil. What menu item did you choose when you right-clicked the Master shape in the stencil?
Adam Lofstedt