A few clients had office Web Apps deployed in their SharePoint 2010 farm. The installation went smooth, services and service application were started. Within the Site Collections the Office Web Apps feature was activated. So far so good.
After a while some test users complained that they couldn’t view or edit documents. When trying to view or edit documents a nice popup box appeared with a correlation ID.
To troubleshoot this problem my first thoughts were that something went wrong with the installation. So I went to the Deploy Office Web Apps page on Technet. (http://technet.microsoft.com/en-us/library/ff431687.aspx#bkmk_underst). Reading through the document, it became clear that the installation went exactly as described on the page. There is a troubleshooting FAQ at the end of the deployment page, but nothing applied.
My next move was diving in to the eventviewer, I found one event regarding to this problem. The event stated that the Service Application Pool account didn’t had dbowner permissions on the content database were the site collections reside. After giving the account dbowner on the Content database on SQL the problem was solved.
So it turns out that when you setup SharePoint with multiple accounts and deploying Office Web Apps that you need to give dbowner permissions for the Service Application Pool account. Todd Klindt has a nice blog about which service accounts can be used to setup a SharePoint farm. Todd also mentioned the dbowner role for the Service Application Pool Accout. Here is the url to Todds blogpost: http://www.toddklindt.com/blog/Lists/Posts/Post.aspx?ID=237