We create an Excel 2007 PivotTable against a cube that contains KPIs, but we
do not include any KPI elements in the PivotTable itself. Excel Services
wont publish it, saying €˜The workbook that you selected cannot be opened.
The workbook may be in an unsupported file format, or may be corrupt.

If however we create the PivotTable against the same cube with KPIs
removed, everything works!