MusicBee 1.4.4393, Windows 7 64 bit, standard DPI value (100%), display resolution 1680x1050.
Download the latest Polish localization file available:
http://www.mediafire.com/?i21f6cz3dxe1f79 and set it in the Preferences. Restart MusicBee.
Use 'Edit' ('Edytuj') command form the Now Playing list ('Odtwarzane') on the right in the default MusicBee view.
The Editor appears with this bug:

The bug exists in Polish localisation file only. I can't reproduce it for English nor Russian.
BTW. Today is my first Anniversary on the forum
I'd like to thank you all for your help and friendly attitude and inform that I won't be available online until mid February. Thanks