Here you have the source file I am using and have kept updated myself:http://bit.ly/mbtranslationsourcefile
Since it was updated many times since the beginning, note that it contains duplicate entries for many elements.
I have been trying to make it a habit of marking the obsolete (oldest) line of these duplicates by prepending them with an exclamation mark. So you don't need to waste time and effort on translating any line that starts with an exclamation mark.
It might well be that the file contains older entries that are now obsolete and not used in current versions of MusicBee anymore, so it would be a waste of time translating those.
But at the moment there is no way of telling if, and what lines are indeed obsolete.
For that purpose it would be good if Steven is able to provide a current and complete listing containing only all active elements.
If he provides you with such a list, please share it?