Need more info-
-are you using soft synth plugs or external modules.
-if external, what MIDI interface are you using? USB or serial?
what version of ProTools? I think you can go up to 6.4.1 in OS X
still with the D24. Do not know about OS 9. Check compatibility on
the digi site, and use the most current that you can. Yer hardware is
a few generations back, when we were all cursing MIDI in PT.
HUH?