This is really strange because after performing all its math calculations, snapObjectToCenter() simply calls pgTBObjSet() to position the objects. Since loading of snapObjectToCenter() occurs farther down in the browser loading sequence, I wonder if some of the PowerPac functions are being called before they are loaded. That would perhaps explain why some things work and some don't. By contrast pgTBObjSet() is among the first functions that become available in the DOM.
However, I'm not sure why your application would be accessing things even before ToolBook gets them loaded up for use.
Clearly, something strange is taking place.