FromVertex (mesh) in Selected mode + Exploder crashes wz4. Bug description and example file are here:
viewtopic.php?f=42&t=1415

It seems like wrote in WZ1 tutorial. CPU calculate green operators, when yellow operators calculated by gfx card. So just use Add operator to solve that problem. (I upload corrected file there in topic)

Great. Thanks very much for that! But anyway such things as populating particles over a selection should work out of the box and imho this issue still needs a proper fix.