I've upgraded to Office 2007 and opened an Excel workbook from Excel 2000
which contained a number of graphs both on sheets and on tabs of their own.
One graph is fine but the others are screwed up because of the way it is
treating empty cells or gaps in the data.

The radio buttons for "treat empty cells as" is grayed out except for the
"zero" option. On the graph that is OK I can choose the option to leave a
gap and its fine.

Does anyone know why this has happened or how I can correct this?