If in the MWE I drop the equation, and don't specify the math font
(below), still get the error, which seems to point to fontspec as the
culprit. Still get the following error:
luaotfload | Font names database loaded:
C:/Users/egc/AppData/Local/MiKTeX/2.9/
luatex-cache/generic/names/otfl-names.lua(load:
C:/Users/egc/AppData/Local/MiKT
eX/2.9/luatex-cache/generic/fonts/otf/temp-xits-regular.lua)
! LuaTeX error ...les (x86)/MiKTeX
2.9/tex/latex/fontspec/fontspec.lua:45: atte
mpt to call upvalue 'check_script' (a nil value)
stack traceback:
...les (x86)/MiKTeX 2.9/tex/latex/fontspec/fontspec.lua:45: in
function 'check
_ot_script'
<\directlua >:1: in main chunk.
\fontspec_check_script:nTF ...ontspec_font","#1")}
\if@tempswa
\prg_return_tr...
l.4 \setmainfont{XITS}
?
Process has been terminated ...
\documentclass[11pt,letterpaper]{article}
\usepackage{fontspec}
\setmainfont{XITS}
%\usepackage{unicode-math}
% \setmathfont{XITS Math}
\begin{document}
Lorem ipsum dolor sit amet, consectetur adipiscing elit. Praesent in
tincidunt nulla. Donec quis laoreet est. Aenean vitae est felis, a
venenatis magna. Mauris semper bibendum vulputate. Etiam bibendum quam
ut erat rutrum consequat.
%\begin{equation}
%\frac{dN}{dt}=rN\left(1-\frac{N}{K}\right)
%\end{equation}
\end{document}
