When I move my cursor over certain areas of my object, the sculptris brush cursor disappears. The windows arrow cursor is still there. The problem is that the ability to sculp is also gone, regarding that area.
Sometimes it is because the brush just becomes smaller in that area - other times it seems like the brush just refuse to enter certain places.
It can sometimes be helped by navigating around a bit.
I have exactly the same problem. The difference is that It's not only some of the times, it is all the time! weird Worked fine before. This appeared after I installed Camtasia Studio. Dont know if it has something to do with it..