Sorry for late response. It is OK now. I have a feeling that it might be due to left navigation window which I disabled a couple of weeks ago. And now no issues. I will try to confirm this later.
I disabled the left navigation window because it seemed to me that the responce was a bit slower for filtered output (I am using single core Celeron 420). And I don't really need it since all selection can be done using music browser in the central frame + Playing tracks frame.
It seems Music Bee is the only music player capable of handling thousands of albums with no significant performace issues. All the others failed miserably. Winamp Library total crash, Foobar 2000 album list total freeze, Media Monkey huge lags, Clementine absolute freeze... just no other can handle a huge collection!
Thank you very much for this excellent software. And if it is true that it is developed using Visual Basic then it shows the real truth about its capabilities.