If you are using Google Play service API for you android Project, and when you try to Export Signed Android Application, you may get such a error message "auth_client_using_bad_version_title". And your res folder may show up errors. Reading the error description gives us some hints.
Description : "auth_client_using_bad_version_title" is translated here but not found in default locale
Issue: Checks for translations that appear to be unused (no default language string)
If a string appears in a specific language translation file, but there is no corresponding string in the default locale, then this string is probably unused. (It's technically possible that your application is only intended to run in a specific locale, but it's still a good idea to provide a fallback.).
Note that these strings can lead to crashes if the string is looked up on any locale not providing a translation, so it's important to clean them up.
Resolving this issue
Depending upon the languages that you have set for your Project you need to place auth_strings.xml files from values folder from google-play-services-lib library folder to you project values folder.
Suppressing this error message
If you want to suppress this error message,
For Eclipse running on Windows OS,
Goto Window- > Preferences -> Android -> Lint Error Checking -> Correctness: Messages
Now Select Extra Translations and make it from Fatal to Warning.
For Eclipse running on Mac OSX,
Goto : Eclipse -> Preferences -> Android -> Lint Error Checking -> Correctness: Messages Now Select Extra Translations and make it from Fatal to Warning.
Now if you try to build your apk for the project folder you will not get this error message, instead it will be showed as a warning.