UPDATE: Nevermind, this is a patch for the "es-us" culture which has the ID 0x540A.

I been trying to track down why I can’t get GRXML files that have ruleref elements pointing to external files working with Windows 7 (64-bit), and ran into the following line of code:

culture = (backend.LangId == 0x540a) ? new CultureInfo("es-us") : new CultureInfo(backend.LangId);

Note the "es-us" locale. Weird. Now back to banging my head against the original problem.