I still get confused sometimes.
But what a boon!
What happened and how do I get it back? Without the colour preview a brush drag-resize is a guessing game.
Why did I turn OpenGL off? Well, with it on Ps crashed continually, the OpenGL features worked, then did not, then Ps crashed. Looks like my GeForce 7300GS 512Mb card with latest 178.24 drivers is not up to the task (especially in a dual monitor setup).