Error in Previous and Next link and translation file

Hi. The link Previous and Next are like this:

I tried to translate and I looked everywhere in the code, but, everything that I found just didn't work.
The problem seems solved when the language selected is English(US), but, when I change to Portuguese (Brazil), the problem returns, so, the problem is the language file, I think. I will look for the translation file to see what changed. Also, there some words not translated yet, like "Registered users" that seems not appear in the language file(.mo).