This is a crash I’ve noticed for ages. When you are working on a partialy visible area of your tool and use the mask, upon feathering that mask zbrush will crash and shutdown!
Anyone else ran into this bug?
yes i have.
so have others here, hope it gets fixed.
http://www.zbrushcentral.com/zbc/showthread.php?t=75234
phew! so I’m not the only one 
thanks for the link spaceboy.
yes, that happens since ages …