I highlighted an issue recently with rendering files to WAV from BIAB 2011 (Build 318)WINDOWS. Someone said the problem was because I was using ASIO rather than MME for my audio driver - changed to MME, restarted BIAB and tried rendering a song - exactly the same result - the real tracks/real drums become out of synch with the midi tracks, BUT only after a tempo change bar. It's as if the real track/drums can't cope with it. Everything works fine on playback direct from BIAB, only on the rednedered WAV file is there a problem. The PC is an I5 with 4 gig RAM, should be plenty powerful enough...