This has been a common zbrush bug for awhile. Looks like its still in 4r8. Unsure what exactly triggers it but occasionally pressing “Reset All Brushes” Button will crash zbrush. Would love to see a fix. Playing Russian roulette with this button is not fun.
When this crash happened i was in the alpha palette making some changes to the new streak settings to a standard brush. When I had finished messing around I hit the reset button and it crashed.