Using Windows 7 In PS CS6 tried 32 bit and 64 bit for the Adjustment Brush. What happens in Camera Raw if I click on the Adjustment Brush and use either the New or Add option I would get either a cross or a double cross and if I hold down the mouse button a very light white would appear on the area I move the mouse over. The Erase option works fine where the dash circle appears and am able to erase.
I uninstalled and reinstalled CS 6 to no avail.
On my laptop all 3 functions of the Adjustment Brush work fine.