Created attachment 27541 [details]
The problematic spreadsheet

I have a spreadsheet which has been created with Apache POI and edited in Excel. (See attached.) When I open it with POI and attempt to add a comment to the first sheet, I get the following error message:

	org.apache.poi.openxml4j.exceptions.InvalidOperationException: A part with the name '/xl/comments1.xml' already exists : Packages shall not contain equivalent part names and package implementers shall neither create nor recognize packages with equivalent part names. [M1.12]

Tested against 3.8-beta4, with the following code:

    public static void bugtest() {
        FileInputStream inp = null;
        
        try {
            inp = new FileInputStream(new File(OUTPUT_FOLDER, "comments-notworking.xlsx"));
            Workbook wb = WorkbookFactory.create(inp);
            Sheet s = wb.getSheet("comments");
            Cell c = s.getRow(0).getCell(0);
            
            CreationHelper factory = wb.getCreationHelper();
            Drawing drawing = s.createDrawingPatriarch();
            
            ClientAnchor anchor = factory.createClientAnchor();
            anchor.setCol1(0);
            anchor.setCol2(4);
            anchor.setRow1(0);
            anchor.setRow2(1);
            
            Comment excelComment = drawing.createCellComment(anchor);
            excelComment.setString(factory.createRichTextString("I like this cell. It's my favourite."));
            excelComment.setAuthor("Bob T. Fish");
            
            c.setCellComment(excelComment);
        }
        catch (Exception e) {
            e.printStackTrace();
        }
        finally {
            try { inp.close(); }
            catch (Exception e) {}
        }
    }