Hi Cris I checked from Polyglot on my site and yes there is the translation 'with image' of and it is allowing to edit.

And there seems no problem in creating new keys.

May be not directly related to your situation but just as some experience and findings on database structure related to languages:

During my Turkish Language module creation I had many problems 

* Before creating the module I did Turkish translations over English module from polygot. This was a wrong strategy from the beginning (and Baloo warned me for this :) )
* When I uninstall English module the the data lists like cities in Turkey (86) or Medical Faculties  (99) on forms module they all lost their titles they were like bx_pre..... something, even guessing what is what becomes almost impossible  .
I observed the database by creating custom form elements and checking where they are registered in database and cache from backup clone site my findings were:
They were recorded to sys_form_pre_lists and sys_form_pre_values

Restoring these to new database was not enough also it needed sys_localisation_keys table restoration. In this table each language has a language key value like English is 3 Turkish becomes 4
Also in cache there is an English language file. This has all the values but restoring this from backup is only creating a temporary full relief if the database is not correct.

After these table restorations now I can install uninstall restore recompile languages and my form titles are not being effected.