Export Crystal report viewer to excel

Hi Guys,

Using the export button on crystal report viewer in IE to CSV format gives me the options to either save or open the file directly and works fine but if I choose Excel it gives me the same Open or Save but if I choose the open option I get "the file is corrupted and cannot be opened " error ?

it works five if I save then open the file, but not if i choose the Open file directly.  

FYI, this funtion works file in my machine or other clients, but not for this specific client.

any help pls?

Thanks