Report created by ReportViewer shows in Excel an error message

Question

If I generate an excel-report, excel 2010 shows the following warning message:

file error: data may have been lost

Note: I already have found the solution and will post it immediately. I make this entry for other people having the same error.

Answer 1

It turned out, that the reports data source had in a value of -0 (negative zero). The datatype was decimal. Excel can not handle this.
The problem seems to lie in the Excel formula engine and not in the report renderer (However I think MS has to solve the problem in the report renderer).

http://connect.microsoft.com/SQLServer/feedback/details/680863/negative-zero-causes-file-error-data-may-have-been-lost-in-excel-2010-when-exporting-ssrs-report

Answer 2

I was facing similar issue where I changed embedded images into external images. In this change some of the images Bit depth property remain as 32 (Click on Property -> Details tab).

I changed it Bit depth to 24 by using imagemagick utility (http://www.imagemagick.org/script/binary-releases.php).

I used "convert -depth 24 oldimage.bmp newimage.bmp" command to change Bit depth property.

And this solve my problem.

I know this is not solution for your problem. But if somebody come across this post while searching that might help them.