Hi:
It really depends HOW you are creating the file for Excel in your stored process. Are you using ODS HTML? Are you using ODS MSOFFICE2K? Are you using ODS TAGSETS.EXCELXP? Also, since you are using a stored process and _webout, do you have the correct STPSRV_HEADER or content-type header for the stream.
If you are using ODS to create your files, then you will need to use a proper content-type header, since ODS creates just an ASCII text file (either HTML or Spreadsheet Markup Language XML) that Excel knows how to open and render.
Sometimes, workbook errors such as you describe happen when you are
1) using TAGSETS.EXCELXP
2) do not have the most current tagset update applied
This frequently is seen when a job will work in a local SAS environment that is running a newer version of SAS but the server (workspace or stored process) is using a earlier version of SAS with a different level of tagset template. Sometimes, I have seen errors when Excel tries to open an HTML or XML file when I have tried to set style attributes incorrectly or inserted some code that might work in HTML, but does not render well when the HTML file is opened in Excel.
Remember that not all client applications on the BI or SAS Enterprise Intelligence Platform can receive output from _WEBOUT -- especially Web Report Studio and the SAS Add-in for Microsoft Office. Especially if you are using TAGSETS.EXCELXP, you cannot execute your stored process from within the Excel pull down menus because TAGSETS.EXCELXP flavor of XML cannot be rendered by the SAS Add-in.
Saying that you use _WEBOUT is a useful piece of information, but it is not the only piece of information needed in this situation. Your best resource for this question might be to work with Tech Support, as they can look at the entire stored process and all your code to help you figure out whether you need to update TAGSETS.EXCELXP on the server or whether you need to do something else (such as use the proper STPSRV_HEADER) in your stored process code.
To open a track with Tech Support, go to:
http://support.sas.com/ctx/supportform/createForm
cynthia