Today one of my support colleges ran into this error when one of the busines users tried to open up an excel document through Office Web Apps.

After a couple of minutes of debugging, it came down to a simple access issue. After running the powershell script below, all seemed to be happy again…

$webApp = Get-SPWebApplication “http://mywebappname.com”

$webApp.GrantAccessToProcessIdentity(“domain\excelserviceaccountname”)