Unable to launch Office Web Apps on your SharePoint 2013 Server –”Sorry, there was a problem and we can’t open this document”

When configuring Office Web Apps for your local development environment, you may run into the following error:

“Sorry, there was a problem and we can’t open this document.  If this happens again, try opening the document in Microsoft Word.”

This error is probably caused by overlooking Step 5 in the TechNet article: http://technet.microsoft.com/en-us/library/ff431687.aspx:

Step 5: Change the AllowOAuthOverHttp setting in SharePoint 2013 to True

On your SharePoint 2013 Server, run the following in your management shell:

$config = (Get-SPSecurityTokenServiceConfig)
$config.AllowOAuthOverHttp = $true
$config.Update()

And it should resolve your problem!