Not all language settings are portable. This warning has the following cause and solution:
When you choose a custom language/country setting for your code, the language conventions used in your code match those set in the Control Panel of your system. You can use custom code locale settings, but your code may not work in other locales or on other systems with different settings. The host application parses some strings based on the Control Panel settings of the machine on which it is running.
If the Control Panel settings on the target machine aren't the same as those on the machine on which the code was written, strings parsed by a host application don't work, for example, code that depends on a locale-specific decimal separator. Therefore, you should not use a custom language setting unless you don't intend to send your code to other users. If you plan to send your code to other users, select a predefined locale.
For additional information, select the item in question and press F1 (in Windows) or HELP (on the Macintosh).