I'm working on a site
http://lang.sottwell.modxcloud.com/
It is based on
this tutorial, using
this context router. I've used this combination before with no trouble.
What is really weird is that while it works great on Safari and Chrome, and even on IE, on Firefox it doesn't work with the default URL,
http://lang.sottwell.modxcloud.com. It produces a blank page with an error
[2014-06-10 22:20:18] (ERROR @ /index.php) Could not prepare context: ru
It works fine if using the virtual subdirectories,
http://lang.sottwell.modxcloud.com/ru/ and
http://lang.sottwell.modxcloud.com/en/.
Again, Safari, IE and Chrome work fine, with no errors.
Figured out what was wrong with it. Needed to add another line to that plugin, in addition to the line I mention in the comments in the gist. Line 124
if($contextDefault == $defaultLang) $contextDefault = 'web';