I think it may be a MIDI synth latency problem, since you report it changing behaviour with the BPM setting, which would be consistent with that.

What are you trying to use for the MIDI output synth at the time?

What sound drivers?

***Sounds like time to revisit the MIDI/Audio output and reset that up to account for any possible latencies. A fat way to do that all at once is to choose that Opt -> Return to Factory Settings and pick the second choice, which invokes the Soundcard/MIDI wizard and then reselect things as prompted.


--Mac