Well, I picked this manga when I saw that its publication ended, but after few chapters I noticed that Chrona gender changed! (No, not the litteral) So, is this intended of the author, or I just missed some translator note somewhere?
Chrona's gender was never revealed in the Japanese Soul Eater manga. There is evidence for both genders but not enough for either to make any conclusive statement. The creator has been asked what Chrona's gender is, but never answered.
In Japanese, this isn't hard to do. Most pronouns aren't gender-specific. While Chrona does use boku (僕) to refer to him/herself, which is a fairly masculine pronoun, it is sometimes used by females as well. However, in English (and many other languages), it's awkward to try to avoid using any gender-specific pronouns. The various different versions of Soul Eater in English use different pronouns, but all of these were added by translators and not present in the original version.
The official Japanese Soul Eater site confirms that this is not known:
which literally translates to "Gender is unknown".
In the anime Crona is exclusively referred to as a "he." However, in the manga "his" gender is purposefully kept unsaid.