When editing a Geodatabase Annotation Feature Class, the following error message occurs:
Object doesn't support this action."
Having the National Geographic Topo! extension installed causes this error message. If the extension is installed on the computer but unchecked in ArcMap, it is still detected by ArcMap, and the above error message is returned. This can occur when either setting the active annotation layer or adding new labels in ArcMap.
Solution or Workaround
Currently, the only solution to this error is to uninstall the Topo! extension.