Working within my VM this morning, and just testing out basic functionality of SharePoint on my demo site. I went to do a very simple task of creating a new document. I received the following pop up.
It took me a moment, but I realised I didn’t have any Office products installed on my VM, however I did have Office Web Apps. I thought I should still be able to create a new document. It turns out that if you disable an Internet Add-On this message goes away. The Internet Add-On is called SharePoint OpenDocuments Class, (which sounds like it needs to be enabled for it to work!)
As soon as I disabled it, without any browser restart, I was able to create a new document.