Hi, I'm a MacTeX 2011 user. I was working on a document that used expl3, then I decided to run the TeX Live Utility to update my installation. After updating I could no longer build my document. After a lot of trial and error I think I've come up with a minimal example to demonstrate my problem: ~~~~~~ \documentclass{article} \usepackage{expl3} \ExplSyntaxNamesOn \ExplSyntaxNamesOff \begin{document} Colons break: boom! \end{document} ~~~~~~ Here are the errors I get when I run pdflatex over that: ~~~~~~ ! Missing $ inserted. <inserted text> $ l.10 Colons break: boom! ! Missing $ inserted. <inserted text> $ l.11 ~~~~~~ PRIOR to updating today, the $Id$ substitutions in my installation indicated I had something like expl3 from SVN revision 2246. That revision worked fine with the above example. My newly-updated version of the LaTeX3 packages as well as the latest version from GitHub both produce the same errors as above. When I use \ExplSyntaxOff instead of \ExplSyntaxNamesOff, or if I copy in the definition for \ExplSyntaxNamesOff from r2246, the above code works. Is this my fault or is this a bug? Thanks, Dale