translation in bookmark mod

Hello.
I've installed flag bookmark module in my multi language website, where the lang support is provided by several modules such as i18n, i18nviews, l10n_client,localize_fields. Despite enabling them, the submodules of flag, like flag bookmarks, aren't translated completely. I've tried different combinations without success

For example in the view which provides user's bookmarks, there's the string "This user has not yet bookmarked any content." (in flag_bookmark.views_default.inc I guess);

in Translate Interface tab I can see that text string under Views (views:flag_bookmarks_tab:default:empty:views:area:content), and it's translated in the different languages, but despite this in the view it appears in English, the default language.

The same happens with flag friend module, where strings like "No friends have been added" are always displayed untranslated, in English

BTW, should the text strings mentioned above be found in the .po file of the flag module? If I'm correct only those with t() should be written there, right? And how does it work when there are submodules like flag bookmark? Is the submodule's translation also included in the main .po file?

Thank you
Kinmen