DataMapper ORM v1.8.2

[eluser]WanWizard[/eluser]
I assume that something in your model overwrites $this->lang. Probably because you have a column called 'lang'.

See http://datamapper.wanwizard.eu/pages/reservednames.html for a list of reserved names. These can not be used for either class properties or column names, either because Datamapper uses them, or because they're used by CI (like this case).