I've been seeing this as well. I've only seen it when I dual box (both maximized) and haven't noticed it when I multi-box 2 or more. My usual setup is one machine main and the second dual or multi-boxing the rest.

I can "solved" it by closing out WoW and relaunching the game. It seems to happen when I launch WoW first and alt-tab out to start KeyClone. It's only done it on my multi-box and haven't see it occur on my main box, but that box is set to transmit only.