"You're not by any chance also using Rebelle 7 are you? It's a buggy mess at the moment. But it seems it *may* be interacting with other apps, including ARV."

Nope. ArtRage Vitae and ArtRage 6.

In any case, I found an incredibly stupid fix which I don't understand, but which works.

In Mac OS, under Displays, under color profile, selecting Cintiq 22HD instead of the default Cintiq Pro 27 fixes it.

As to why, I have NO idea.

Cheers, and thanks for the help!
-D