ERROR: Primitive ' SCView New' failed. Operation cannot be called from this Process. Try using AppClock instead of SystemClock.

On Mac (using the "Cocoa" GUI) you can't do GUI things like plot a graph or create a window unless it's happening from the AppClock. So if you run this manually, it works:

GUI.cocoa; [4,6,5,7,6,8].plot

but this fails:

GUI.cocoa; Task{0.3.wait; [4,6,5,7,6,8].plot}.play(SystemClock);

and you get a similar problem if you're calling the method from an OSCresponderNode or almost any asynchronous method.

The fix is to wrap the .plot call (or whatever) in { }.defer.

For more info see the helpfiles "Understanding-Errors", "GUI-Overview".