I´m following pixologic tutorials and when was making the alien helmet (the tutorials are in Zbrush 3.5 and i got the 4.0 version), i started to have some problems with the geometry option, cause when i work with zpheres, this option change, and even when i use unified skin to get the model back to poligons, geometry still don´t allow me to uso options like Group from polypainting, or group loops. When i start the program, all of this options are avaible (there´s geometry and geometry hd), but geometry changes when i start working with zspheres.
are you at your lowest subD level?