Embedded Spreadsheets not displaying

I recently had an issue with Excel spreadsheets that were embedded in a page not displaying. Instead of the spreadsheet, users saw an error box with the message “Unable to load the requested workbook.” Users could open spreadsheets in the app, but not in the browser (we have Office Web Applications configured).

There are a lot of reasons why this is happening. Usually Excel Calculations Services is not running. Recycling the application pools in IIS can often fix this issue. But not this time, not for me.

Digging deeper, I went to the ULS logs. I found an interesting error: “#960013: Antivirus scanner timed out.” associated with the page the spreadsheet was hosted on.

We run Forefront Protection for SharePoint on our farm, so I opened up the console. I found the following error: “The SharePoint service is running but the Forefront VSAPI Library is not registered.” Forefront runs on each server on the farm, and this error was only showing up one of the farm servers. Of course it was on the application server, where Excel Calculations Services were running.

Some Googling led me to this: http://blog.karstein-consulting.com/2010/12/07/forefront-protection-2010-for-sharepointerror-the-sharepoint-service-is-running-but-the-forefront-vsapi-library-is-not-registered/ , but the steps listed there to restart the service did not fix the issue. Finally, a reboot of the server got Forefront into a good state, and spreadsheets started working again. Why didn’t I try that first?