Do you have any customizations (Startup Suite in the APPLOAD dialog, ACADDOC.lsp file, some other method) that run every time you open a file, that attempt to enforce a standard? Could that customization be defining an office-standard Dimension Style, that happens to have the same name as the one you use, but that has "leaders on" for moved text?
David Koch
AutoCAD Architecture and Revit User
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