What is this icon in the menu bar?

[SpitUK]

The one with a cross through it between Evernote and Alfred? It has appeared over the last few days and when I click on it nothing happens. Don't remember installing anything new or doing anything differently.

 

[Altemose]

The one with a cross through it between Evernote and Alfred? It has appeared over the last few days and when I click on it nothing happens. Don't remember installing anything new or doing anything differently.

Image

If you hover over it, a small box will appear describing it. Er. That should happen.

 

[SpitUK]

Nothing happens when I do that, it tells me for all the others.

So strange.