I think i found a bug
specs:
MacPro 2009 / Osx 10.10.5
zbrush version 4r7 P3
32 & 64 bit version (error occurs on both versions)
issue:
EdgeLoop / Delete Loops & Align Loops -> zbrush crash
Many thanks. I can confirm that this happens on Mac OSX and the development team is aware of the problem.