I experienced runaways and had no idea what was going on. I noticed that holding shift passes every key to the other clients. My autoloot is set to shift. What was happening is I was holding shift to autoloot, and accidentally hitting my forward key, then switching to another window. This caused it to pass "shift+w" to all the clients, when I switched windows I had never released "shift+w" so all my characters kept running.

To make them stop I simply hit "shift+w" again. Only happens when I'm not paying attention, no biggie