SharePoint – Word Web App cannot open this document for viewing because of an unexpected error

Today I saw a strange error with office web app. I was unable to open up any of the office documents in office web apps. Clicking the document link simply throws following error

I search ULS log files and found following exception details

System.AccessViolationException: Attempted to read or write protected memory. 
This is often an indication that other memory is corrupt.

To resolve this I execute following steps. For simplicity I am using Word as an example.

1. Ensure Word Viewing service is started
   • Central Admin -> System Settings -> Manage services on server -> Word Viewing Service
   • 
2. Stop the Word Viewing service and start it
3. Ensure Word Viewing service proxy is created
   • Central Admin -> Application Management -> Manage service application
   • Look for following
   • 
4. Ensure Word Viewing service proxy is associated with proxy group
   • Central Admin -> Application Management -> Manage web applications
   • Select the Web Application. From ribbon click on Service connections
   • 

This resolved the issue and I was able to open up office documents in office web apps.