Hi I've just got Zbrush and I'm having a problem with masking. Watching a tutorial on the web the instructor does the following:

Creates a 3D plane and makes it a polymesh.
Activates symmetry in the X and Y on his plane. (So that he can draw from four points)
He selects a dragrect stroke and alpha 28.
Then he presses CTRL and drags from the centre of the plane and makes a square mask inside it.

However when I do that when I press CTRL it changes my stroke from dragrect to freehand.

The tutorial is done in 3.1 and I am using 4R6.

How can I stop this happening?