You cannot click both "Show Values" and "Show Labels", and you cannot show the category labels in Microsoft Excel 2008 for Mac

Consider the following scenario. In Microsoft Excel 2008 for Mac, you open a Microsoft Windows version of a Microsoft Office Excel workbook. The workbook contains a chart. The series in the chart uses labels that show the category, the value, and the series name. The labels are visible in the chart. You right-click a series, you click Format data series, and then you click Labels. In this scenario, only Show Labels is selected. For charts, you cannot click both Show Values and Show Labels. Additionally, you cannot show the category labels.

If you click Labels or Values on the Labels pop-up menu, the category label on the chart disappears from the series.

Note The Labels pop-up menu is under Other options in the Chart Options area on the Formatting Palette.

Microsoft has confirmed that this is a bug in the Microsoft products that are listed in the "Applies to" section.