The selection includes the series labeled with an x in the row or column heading. You cannot delete the series plotted on ...

The selection includes the series labeled with an x in the row or column heading. You cannot delete the series plotted on the x-axis, because the series is used to calculate the scale for the x-axis of your chart. To correct the problem, try one of the following:
* Select another series, and click Plot On X-Axis (Data menu).
* Select a chart type other than xy (scatter) or bubble.