Special characters in messages

I am working on Spanish translation of the messages of Mango.
I have a problem with special characters. For example, the & _aacute; show up well on some messages and not others.
Looking at the translation to Portuguese (with Notepad), I saw the special characters have other representation. What format are they? Is there any program to edit?
Thank you very much.

The translations files are encoded in UTF-8, and yes, HTML entities should not be used. (UTF-8 is non-standard for Java resource bundles, but was necessary to support Chinese.)