Latin extended letters (Lithuanian) are not rendered correctly in form fields

Hi all, i have this weird problem where i need to set up a fillable forms document in Acrobat. However none of the Lithuanian letters are rendered correctly, no matter which of the original embedded fonts i choose "Helvetica, Courier, Times new roman" - anything i choose "above the underline" in fonts for fields produce weird missmatch when forms are filled, even though these fonts are used successfuly everywhere else - word, websites, you name it. What could cause these problems? Some of the letters are skipped completelly and do not render at all.