Thanks rharv. I've unchecked the input monitoring and as you suggested, it has made no difference.
In my MIDI output drivers I have SB X-Fi Synth A and Synth B selected. My default DXi/VSTi synth is CoyoteWT and I have 'Re-Route MIDI playback to default' checked.
As you have no doubt already realised, my technical know-how is somewhat limited so ASIO buffers are a bit of a mystery to me, however, I hope this answers your question. In the ASIO audio drivers window, Preload Track Buffer MS is set at 2000. In the Creative ASIO driver control panel, ASIO Buffer Latency is set at 40ms, which is the lowest option it offers.