When trying to open a PowerPoint presentation or an Word document stored in SharePoint using the PowerPoint / Word WebApps you might face the following issue:
When I saw this error I felt like there is an error in the matrix (dejavu) not only in front of me.
Looking over my shoulder for Neo I was checking the eventlog I found EventID 3760
I had an issue like this before (described in this blogarticle:Excel calculation services–The Workbook can not be opened)
When applying the script mentioned in this article and performing an IISreset the issue got resolved.
The concerns highlighted by me in the above mentioned article are still the same (and to be honest have even been boosted)
So I will have to include all service accounts running my Office WebApps to the script which I use to create new Content Databases in the future.