BI 7.0 Work Book corrupt error

Hi

We are working in BI7.0 and latest Excel version. Business user has created some workbooks and they were running fine. Recently she made some changes and saved. Since then the WorkBook got corrupt and giving following message. BI 7.0 version and Excel version looks good. Can anyone please make suggestions to overcome this issue.

Diagnosis

BEx Analyzer has tried to open a corrupt workbook. Excel cannot open this file.

System Response

The workbook will not open. A message will appear.

Procedure

Contact the author of the workbook. The problem may be due to a more recent Excel file format.

Procedure for System Administration

Thanks