Bcz AbanteCart uses some strange way of storing language strings, u should use the bugged build-in Translation tool and to backup your work daily.
If was in INI or GNU Gettext POT files, can be done with Transifex....
and on to current topic, the cart otherwise is better then most, just wondering who mind**** decided to use XML without to check rest alternatives ? did u asked yourself - will we go for multi-lingual support ? even OpenCart which looks like base for this one, uses better way for handling language files....