I did it!

Thank you very much. I just changed this:

Original

[user_edit] (Line 559)
edit_user_name = Nombre de usuario:
edit_avatar = Avatar:
add_avatar_link = anadir avatar
edit_avatar_link_title = editar avatar
edit_user_type = Tipo:

Later

[user_edit] (Line 559)
edit_user_name = Nombre de usuario:
edit_avatar = Avatar:
edit_avatar_link = Editar avatar
edit_user_type = Tipo:

And then...

Could I help you to translate the forum to Spanish? It would be a pleasure for me.