"Add-in Manager" untranslated/misterious strings

Binary package hint: f-spot 0.5.0.3-1ubuntu6 (jaunty)

I'm part of the Guadalinex distro developers team and one of our prior tasks is to make a full Spanish distro. In the task of getting 'f-spot' fully translated, I have found a really weird case that I haven't been able to resolve...

The matter is that there are some strings in the 'Preferences/Manage Extensions' which remain untranslated. We can find, for example:

* Add-in Manager
* The following add-ins are currently installed:
* etc...

I check that the 'f-spot' translations are managed directly from package source, it's not included in any langpack, so I went to look into f-spot code/.pot/.po.
I started looking for those strings I mentioned, but I could'nt find them nor in the code neither in the .po files...
I realized that those strings were correctly translated in .po files, matching correct source strings, but they were not being displayed translated.
I checked that "Add-ins Manager" is now substituted by "Extensions Manager" mostly everywhere in code and that made me wonder if strings in code (in English) were being showed in GUI as they were in code... And they weren't!!

I'll illustrate it with some examples:

* es.po

#: ../mono-addins/Mono.Addins.Gui/gtk-gui/Mono.Addins.Gui.AddinInstallerDialog.cs:36
#: ../mono-addins/Mono.Addins.Gui/gtk-gui/Mono.Addins.Gui.AddinManagerDialog.cs:58
msgid "Extension Manager"
msgstr "Gestor de extensiones"

* mono-addins/Mono.Addins.Gui/gtk-gui/Mono.Addins.Gui.AddinInstallerDialog.cs:36

            this.Title = Mono.Unix.Catalog.GetString("Extension Manager");

* String showed in GUI when launching f-spot (even launching it in English)

"Add-ins Manager"

It is a really weird case... At least until I knew where those strings are coming from :]