DP3 Mystery MIDI noise

[seekir]

After purchasing a MOTU 828 and recording audio with no real problems, I've been recording MIDI with Digital Performer 3 for the first time and an odd, intermittent clicking sound is spoiling some of the tracks. I'm unsure of the source of these high frequency pops which seem to appear randomly on the MIDI tracks. I'm working with a DP3 file with 5 audio tracks and 3 MIDI tracks. I've noticed the isolated snapping noises while playing the Fatar SL-161 MIDI controller keyboard using the built in Mac Quicktime instruments and listening through the MOTU 828 even while not recording. The noise appears in the recordings as well. If I mute the suspected recorded "bass" MIDI track which seems to generate the noise, the clicking is no longer audible. Oddly, muting the audio vocal track also causes the clicking to disappear.

I'm also confused by the MIDI panning process - using the pan pot in the mix window does not seem to affect the position of the MIDI voices in the stereo image. The sound seems to remain centered even with the pot or knob in the mix window fully rotated right to 128.

System: Beige Mac G3, 0S 9.04, 256MB RAM, Motu 828, Keyspan firewire card, Fatar SL-161 keyboard controller, Quicktime instruments, Macman MIDIMAN serial interface.

Any help will be much appreciated.

Mike