OBIEE 11g : Exporting Dashboard Page to Excel Error:"Excel found unreadable content in" FILE_NAME.xlsx. "Do you want to recover the contents of this workbook?"

Scenario:

When you try to export a dashboard page or entire dashboard from "Page Options" on a dashboard to excel 2007 or excel 2003 you can get the excel file with out any error, but when you try to open the exported excel file then you will get an error message related to unreadable content. The same happens when you create an agent to deliver the dashboard page. 

  Root Cause:

This issue may be caused when Dashboard Page name is using special characters that are not acceptable for Excel Sheet Name.
For example

 =

\
 /
 *
 ?
 :
 [
 ]  

& 

;

 Resolution:

Rename the dashboard page and avoid the special characters. Now export it to excel and test. You can see the excel file opening with out any errors and data will be shown as per the dashboard page.