this just happened to me.
i was doing a lot of guesswork at the time on my own project, so i really had no idea what caused it.
after some research to narrow down the problem, for me i've fixed it by keeping my number of open tabs in Unity to under seven.
this may be why some people have had success in undocking tabs and creating windows out of them.
i think it's not the interaction between the tabs themselves, but how Unity manages those tabs.
if Unity is trying to reference the tabs, and simultaneously remove one or more of those tabs from the container of tabs it has referenced, it is unable to do so, and will crash.
i'm not certain if this is a Unity or Playmaker issue, as i'm not going to begin to understand how it *actually* works. i'm satisfied with just surmising enough to keep me out of trouble, so that i can work on my own problems.
hope this is helpful to anyone who may encounter this problem, and hope this solution works for people other than myself.
happy coding!
**edit**
i don't know, maybe it's late and i just jumped at the solution. i think the premise is accurate, but my solution is not, since after posting, i decided to *waste my time*
by doing further checking.
by adding another open Unity tab, i couldn't repro the error.
seemed that having the Globals variable Playmaker tab tabbed behind the FSM window was what did it.
anyway, it's obvious that i'm shooting in the direction of the problem, there may be something helpful here, or another way of looking into the issue, so i'll leave my post up, and hope it helps.
