try listening to a song. (Misc. -> Midi Info... -> Listen) and the song while one is playing and hit listen, it will NOT change songs till you hit listen a second time.
this may be related to the slow drawing, if i click quickly (i see the button get pressed) then it wont work, if i hold it down for a second then it will play on the first press.
EDIT: it occurs with everything, if it doesnt have focus then a quick click is ignored.