edmFile.RenameEx causes eDrawings "<file> was not found" prompt

Does anyone have a suggestion how to resolve this issue?

I've written (copied, mostly) an add-on for EPDM which generates a serial number and renames a file; however, whenever this is executed the user sees a prompt from eDrawings: "C:\<filename> was not found". Is there a better way to do this?

(Code abbreviated. This is written in C#)

                                //rename the file

                                edmFile.RenameEx(poCmd.mlParentWnd, generatedSerialNumberValue + "." + fileExt, 0);

                                //Update part number in the data card

                                IEdmFolder5 edmCurrentFolder;

                                var currentFile = _currentVault.GetFileFromPath(edmFile.GetLocalPath(edmFolder5.ID), out edmCurrentFolder);

                                currentFile.LockFile(edmFolder5.ID, poCmd.mlParentWnd);

                                IEdmEnumeratorVariable5 enumVariable = currentFile.GetEnumeratorVariable();

                                enumVariable.SetVar("Part Number", "@", generatedSerialNumberValue);

                                enumVariable.SetVar("Part Number", "Default", generatedSerialNumberValue);

                                IEdmEnumeratorVariable8 enumVariable8 = (IEdmEnumeratorVariable8)enumVariable;

                                enumVariable8.CloseFile(true);

                                currentFile.UnlockFile(poCmd.mlParentWnd, "Auto-Update Part Number");