I recently reinstalled MacTex on my mac (OS 10.8.4). The distribution of TexShop is new, version 3.26. For some reason, xelatex and lualatex have disappeared from the pull down menu of tex options. I've tried putting these lines at the top of the files:
% !TEX TS-program = xetex or % !TEX TS-program = xelatex
but my papers still won't tex. I've checked the path, there is a copy of xetex (xelatex) in that location. The paper will tex on a different machine which mysteriously has xelatex in the pull down menu. Can anybody help me to turn on that option?