Steps to reproduce the error:
1) Open a clean 6.0 portal and enable staging (any type).
2) Change the default portal language form English (en_US) to e.g. Italian (it_IT)
3) Create an arbitrary structure (with a belonging template) and a web content based on it. Do not publish to live.
4) Observe that in the database neither 'content' nor the 'title' of the Web Content is localized.
5) Shut down the portal and upgrade to 6.2.
6) Add an en_US translation to the structure to avoid StructureNameException
7) Make sure the portal default language is still set to Italian (it_IT).
8) Attempt to publish the article to live.
Publication fails with LocaleException (full stacktrace is attached).