I tried the new release of AstroPlayer Nova 1.143 today on my ICS phone. The unlock screen was coming up if I pressed the BT control while playing and the screen was dark. HOWEVER: when I disabled the AstroPlayer unlock screen, all is well - I can start and stop playback with my BT controls, no matter if screen is lit or dark, if AstroPlayer is displayed or if I press Home button and only see my home screen.
So you did a good job anyway, Viktor. The unlock screen issue is a minor bug to me, as one does not need it when playing and controlling the player over Bluetooth.