Symptoms:Web Apps 2013 is installed and a separate SharePoint 2013 farm is consuming it. Configuration all looks normal, but the Web Apps funtionality within SharePoint is as follows:
- Excel - funtioning
- OneNote - functioning
- Word - can create a document with Web Apps, but cannot preview or edit in the browser
- PowerPoint - can't create, preview or edit in the browser
Sorry, there was a problem and we can’t open this document. If this happens again, try opening the document in Microsoft Word
You find this in the event logs:
"Could not load file or assembly 'Microsoft.Build.Utilities, Version=18.104.22.168, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies. The system cannot find the file specified"
A fiddler trace reveals that the file can't be found (exactly what the event log says), but looking on the server shows the file is there.
w3wp.exe (0x1CF0) 0x280C Office Web Apps Office Web Apps common af46w Medium WACServer HttpModule: Completed request with status code  f068034b-e1ca-4676-b391-2a0143212c80
I followed this article for changing security for Web Apps after a server has been security hardened:
I followed this article for tyring to make sure the server is healthy: http://www.wictorwilen.se/office-web-apps-server-2013---machines-are-always-reported-as-unhealthy
But none of those things worked.
Issue:The server had been security hardened and some settings that were changed were non-standard.
Solution:In my case, the thought that it was a permissions issue. Permissions were causing part of the functionality to fail. On the Web Apps servers:
- Open the registry editor (type regedit in the search).
- Expand HKEY_LOCAL_MACHINE
- Right-click on SOFTWARE and choose Permissions
- Click on Add...
- Click on the Locations... button.
- Scroll to the top and you should see the name of the server you are logged into. Select it, then click OK.
- Under Enter the object names to select box, type Users and click on Check Names. Click on OK.
- Click on the box next to Read, then click OK.
This resolved the issue for me.