Power Point :: SharePoint Feature Failing After Site Collection Was Backed Up And Restored

I setup PowerPivot (PP) for SharePoint and activate it on few site collections in production environment; I upload a PP workbooks in a library, manage the data refresh schedules, run the data refresh for an external SQL databases, etc. Everything works fine for several days. One day we decide the move one of the site collections (X) from its current content database to its own (new) content db. The way we did it is that we took the site collection backup in production, restored it in test environment (in its own content db; we deleted the old site collection in test first before restoring), checked everything including PP data refreshes etc.; all worked fine.Then we did the same thing in production - we deleted the old site collection X, restored the site collection from the same backup file that we used in test environment, everything works fine EXCEPT the PowerPivot refreshes!! :-(

I am getting these errors: When I click on the workbook, it gives this error "An error occurred during an attempt to establish a connection to the external data source. The following connections failed to refresh: PowerPivot Data".When I click OK on error dialogbox, it opens the workbook fine but no slicers/refreshes work now. When I go back to the library and click on "Manage PowerPivot Data Refresh" to open the refresh history/schedule page, it gives this generic but scary error: "An unexpected error has occurred. Troubleshoot issues with Microsoft SharePoint Foundation." ULSViewer or Event viewer is not showing anything related to this error!Strange thing is that PP refresh works fine in Test environment, as well as on other site collections in production that we didn't touch (which tells me there is nothing wrong with my PP configuration). Did the backup/restore in prd cause anything? Did moving it in its own contentdb cause anything? (But then why it works in test environment?) Is there anything wrong with site collection PP feature.