Bizarre translation behaviour

My site is in pt_BR, I installed the translation files in /languages and it works fine but some strings are not translated.
In the page I submitted, for example, “Register” and “Lost Password” remain in English.
To check if there is a problem with the translation files setup I hacked class-theme-my-login-template.php to print out the output of __(‘Lost Password’, ‘theme-my-login’) and __(‘Register’, ‘theme-my-login’). These seems to work, but in the end it keeps spitting out the English version.

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