This error occurs when GN4 discovers a problem when loading a schema, possibly a wrong opCode value specified.

To correct this error

Open the related schema, locate the error position and then correct it. Then, retry to reload the schema.

See also http://tech.teradp.com/tech/html/gn4/docs/VSdoc/index.html#frlrfTeraDPGN4CommonOpCodeClassTopic.html for the list of valid opCode names.