I did a quick search and noticed that there were some problems with clipping plane back in early June and maybe this is related. Previously when I created a clipping plane it would effect all views or you could toggle the plane on or off in any given view. Currently creating a plane will only effect one other view, EG creating in Back will clip Top and creating in perspective only effects perspective.
Hitting the clipping on button will only create a new plane, not toggle an existing one. Am I missing something or is this a bug?