In some places of GUI polish characters (ą, ę, ś, ź, ż, ć, ń ...) are not displayed properly. On these screenshots I marked badly displayed words with red color and words that are displayed correctly with green. This is only an example, that problem appears in many other places of program.
Windows 7 Ultimate SP1 x64
FlashFXP 4.2.2 (build 1760)