Just updated to Xcode 5 and this is the first error its throwing on the logger for all my apps. Can\'t seem to understand why this is happening.
2013-09-
I had the same problem and solved it setting the 'Localization native development region' to match my systems region. In my case from 'en' to 'de'. The referenced files are stored in localized versions in your filesystem. So this setting is used to identify the needed version.
You can find that setting in your project settings at 'Info' -> 'Custom iOS Target Properties'.