Did two searches about this on ZBC, here are results:
Sorry - no matches. Please try some different terms.
Here is a page from the online docs:
http://www.pixologic.com/docs/index.php/Using_the_MatCap_Tool
Can someone please notify the powers that be that the online docs are messed up? Kinda leaves us mac users at sea.
Zbrush 3.12B on a Mac Mini with 3gb RAM