I've also created an extension including a translation which I can't get to work. I'm using the i18n operator, however, since the x18n is deprecated since v. 3.2 (http://ez.no/community/news/ez_publish_32_beta_1_released). Still can't get it to work though.
I've had the same problem. I have an extension called arkiv. The translation for this extension is placed here: extension/arkiv/translations/nor-NO. I'm using the i18n - operator. The reason my extension-translation didn't work was this:
In settings/override/site.ini.append.php, this line needs to be added: