Data Refresh Failed in Excel Services

I prepared a SharePoint Report Center portal by using SharePoint 2007 recently, but I was unable to refresh the Excel workbook on my portal and got an error message:

I'm sure my data connection and document library are trusted and I can view the workbook without problem. Here is my detailed situation:

Enable Excel services and workbook refresh functionality
Upload an Excel workbook to a document library
Add a Excel services webpart and point to the newly uploaded workbook
Excel workbook render correctly
BUT, an error occur if I click "Refresh" button on the top menu
Thanks to my friend Qifeng, he told me that it's related to security restriction and execute three commands. Finally it works:

1. stsadm -o set-ecssecurity -accessmodel delegation -ssp sspname
2. stsadm -o execadmsvcjobs
3. iisreset

Comments and queries available here

You can find other solutions at following site,

http://patrikluca.blogspot.com/2008/10/data-refresh-failed.html

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