Hi Steve,
Thanks for your continued suggestions. I may have found the solution: Earlier in the same Sound On Sound article a problem of consistent MIDI latency which affected the actual recorded MIDI was mentioned. This differed from my problem of course but I tried the solution as a last resort before you replied with your latest ideas.
The fix involved using windows explorer to navigate to a folder called midiportenabler under: Program files\Steinberg\Cubase SX3\ and then cutting a file called ‘ingnoreportfilter’ out and moving back into the parent folder 'Cubase SX3' and pasting it there. Then I ran Cubase SX3 and opened up one of my projects. Now, when I went into one of my MIDI tracks and clicked on the dropdown boxex for MIDI ins and MIDI outs there was a new option: ‘M-Audio MIDI in (emulated)’ and ‘M-Audio MIDI out (emulated)’. Selecting these new MIDI in and out options for a particular channel made the live jitter problem go away. Selecting the original options again made it reappear sometimes.
I’m still reluctant to celebrate too early due to the intermittent nature of my problem but so far it seems to have worked! If it still goes wrong then at least I still have your recent ideas to try out.
Thanks again Steve!
Michael