You obviously have a setlocale() command somewhere in your code which isn't very happy at what it is being passed 🙂
The correct format is this:
setlocale (LC_ALL, 'country_suffix');
Where country_suffix = the locale required.
OR use this:
setlocale (LC_ALL, '');
Which will instead pick up the browsers environment setting locale and use that as the base.
Cheers,
Rich