Been one of those rather frustrating weeks - mostly caused by language issues...
Apparently under most reasonable settings #Sitecore
likes to look for #Language
variants at the beginning of your URLs (i.e. /en/SomePath/ and /de-de/DasBoot/ etc.) this usually works fine - unless for some reason you want a path like "/my/email-preferences/" (because you're setting up a user profile area) and your machine (thanks Windows 8) appears to have knowledge of the Burmese language.
Sitecore therefore keeps setting the language to "my" and then trying to find "email-preferences" in the root of the site and returning a nice blank page (because strangely I don't have a Burmese version of my UK investment bank's website).
I'll probably have to move this to some variant of www.example.com/my-example/email-preferences
to attempt to not fall into this.
Alternatively (as a temporary fix - we're bound to reach out to Burma soon) I could override the StripLanguage preprocessor and only return matches for languages that have been configured in Sitecore...