Many of our users have had difficulty setting up multilingual sites because of the way Ubercart allows users to set strings through settings forms. Some examples are the titles of blocks, Ubercart cart/checkout buttons, and address labels. Because these strings are stored in the database, they are not normally translatable by Drupal.
The way around this is to use the Internationalization module for Drupal. Through this process described in the module documentation, you can tell the module to mark variables stored into the database for multilingual translation.