I use software called "Actual Window Manager" When it is active and working on the Sculptris window; it displaces the cursor for the brush a bit lower than the mouse pointer which makes for an odd user experience at least with my hardware and software configuration (Win7x64).
If others have this software installed or other software from Actual Tools, and are experiencing troubles. The solution that worked for me is simply to add Sculptris to Actual Window Manager's exclude list. May be worth adding to a known issues section if there is one for Sculptris. I'm brand new here, but I wanted to help if anyone else was having that frustrating experience.