freyrheidar
Hi
Kindly check it now, Seems there is issue in the DB, updating Joomla fixed it,
Please update the template and T3 plugin with all Joomlart extension to latest version.
Older version may have issue with latest Joomla.
Take a backup of site, before updating extensions and template, If there are custom hacks, they will be override in template update.
Regards