[NTG-context] MkIV : MTXrun | unknown script 'context.lua' or 'mtx-context.lua'

I followed all these steps to install MkIV on a Mac and to run it with either Smultron or TexShop : http://wiki.contextgarden.net/ConTeXt_Minimals/Mac_Installation However it works fine with Smultron (but I am more used to TexShop to run TeX files), with TexShop I get : MTXrun | unknown script 'context.lua' or 'mtx-context.lua' Even after running the following command line : luatools --generate it doesn't help at all. Thanks for any hint, Mathieu