Not Seeing Strings Added by i18n Modules

I have installed the i18n modulules, and enabled several of them - ie., multilingual blocks, multilingual menus and multilingual profiles.

1) I add a custom field to my users' profiles - defining custom name for the field, custom description, etc.
2) I go into Site building -> Translate interface -> Refresh, and I refresh all strings (and just for good measure, also update all translations)
3) When I visit a user's profile page in a non-default language, I would expect the l10n client module to pick up the new strings for the new fields and their descriptions - but it doesn't. Those strings are never listed.
4) If I go to Site building -> Translate interface -> Search, I can find the untranslated strings, and translate them there.
5) I can visit a profile page in a non-default language, and see that my translated strings actually appear, and are being used - however, they NEVER appear in the l10n client's list.

The same seems to apply to other modules - ie., if I change the name of menu items, or blocks - that is, I can translate the new strings by going searching them manually through Drupal's standard 'translate interface', but l10n client seems totally unaware that the strings even exist.