This Happens to me on a fairly regular basis as well. One computer, usually only one Discourse tab. (I only open a new tab if I think that a side topic is going to take me down a rabbit hole)
I only see it when I am logged in, but it can show up randomly as I navigate around the forum.
Win 7 pro, latest Chrome.
Though, to be fair, I think that what @ChaoticLoki and I are seeing is different from what the OP was describing. I also thought that there was a bug post on it already, but I can’t find it right now. Is there anything that I could try (Client-side. I don’t have a Discourse instance to play with.) to help pin down whether this is bad data being sent from the server, or if the ember app is glitching in its rendering?