This kind of error only happens occasionally and under specific circumstances. The major problem with it, as it states "something has reinstalled our exception handler", it does not state what has reinstalled the exception handler. So it's almost impossible to pinpoint. It could be to do with the location, plugins that are running, or some other kind of random element. If it keeps happening repeatedly, I'm afraid the only other thing left to do is to remove all plugins (except Gizmo), and re-try, while adding the plugins back, 1 at a time, and trying each time until it happens again. That will tell you if it's a plugin related issue.