Nobody else has been able to reproduce it, and you haven't given enough information on what you're doing or what you've tried. Have you tried different machines? Different browsers? Have you tried pressing the various buttons in the UI? What kind of machine do you have? Do you have a very small amount of RAM? Et cetera.

You might say your browser works fine, but I'd put my money on something there being the issue.

I saw you tried different versions on 2 different machines -- it certainly suggests something related to your setup: I can zoom, open in new tab, save as, etc on Firefox 41 on Ubuntu 14.04.

Do you have running app for mouse gestures? That's the only thing I can think of that makes sense in your scenario. Try holding the right click for a few seconds, see if the context menu appears.