Diagnosis
In the settings for the planning layout, you have defined that theExcel worksheet should be read as an HTML file and saved(provisionally). This is not possible.

System Response
The Excel worksheet is not available as an HTML version in the WebInterface Builder.

Procedure
A worksheet can only be saved directly as HTML as of Microsoft Excel2000. Check your Excel version. If you have Excel 2000 or higherinstalled and the problem still occurs, then check your Excelinstallation.
To proceed it is possible to deactivate the option "Save as HTML" inthe Layout Builder, remove the problem and save the layout again later.