The commit that git bisect lead me to and the diff between the pdflatex .tex files of before and after the following commit (which is the same as the diff between the output from before and current trunk) is pasted below. After adding the English class option and adding babel to the preamble, the export works fine. Is this what should be done to the document or is it an internal issue?
Scott commit 566a5f2b7513ffbd75cc92f713dccccc2636f37e Author: Juergen Spitzmueller <sp...@lyx.org> Date: Mon Jul 23 11:36:55 2012 +0200 Fixes to the language package call * Assure that really no language package is called when none is selected. * Only call global custom package if global is desired. This is a candidate for branch as well. [diff from before and after when exporting to LaTeX (pdflatex)] -\documentclass[12pt,a4paper,english,cjk]{book} +\documentclass[12pt,a4paper,cjk]{book} \usepackage[T1]{fontenc} \usepackage{CJKutf8} \setcounter{secnumdepth}{3} \setcounter{tocdepth}{3} \usepackage{color} -\usepackage{babel} \usepackage{pmboxdraw} \usepackage{graphicx} \usepackage{setspace}