When opening Excel outputs an error is displayed.
If the output is 2002 it is ok after Excel opens.
If the output is 2007 then Excel tabs will be named Recovered_SheetX
Errors when opening Excel outputs:
The file you are trying to open, 'filename', is in a different format than specified by the file extension. Verify that the file is not corrupted and is from a trusted source before opening the file. Do you want to open the file now?
Excel found unreadable content in 'filename'. Do you want to recover the contents of this workbook? If you trust the source of this workbook, click Yes.
The report name page is too short or the report name is too long.
Resolving the problem
Edit the report in Report Studio:
Go on Page Properties, then Miscellaneous section and change the Name property to be a minimum of 5 characters or a maximum of 31 characters.