MIDI notes random delay

I finally decided to try the MIDI functions on ProTools (6.7cs7) but ran immediately into a major problem. I'm getting randomly delayed (not stuck, just briefly delayed) MIDI notes on the simplest of MIDI tracks. In my current session I have 3 tracks, only one playing where the problem is and that track is playing a simple RH quarter note piano part. The delay is around a 16th note or an 8th note or so. The delay is random but quite often (doesn't necessarily occur at the same spot twice). Usually the entire chord is delayed, not just one note. I did a big Digital Performer (4.52) recording yesterday with 30 tracks or so of MIDI and no glitches in timing. With this problem ProTools session I saved my MIDI tracks as standard MIDI files and moved the audio tracks from the session to Digital Performer (thereby recreating the song in DP) and there are no timing issues whatsoever. Any hints? These are quite noticeable glitches, we're not talking subtle timing issues here. By the way the track is playing an external synth unit, not a software instrument. Mac OSX 10.3.7 G4 dual proc 800 MTP AV USB (two networked together though I tried turning off one) ProTools HD2 6.7cs7 ditched all ProTools/DAE prefs and restarted. Didn't help. tried changing the synth module the track was playing, same problem on another synth.

I've had this, too, in 6.7, it comes and goes. Ed

out of curiosity: what is your midi interface?

Hey, I'm on A Win XP pc with an HD3 PT 6.7cs7 setup and I'm getting the same thing. At first I thought I was loosing it because it wasn't that noticeable until I rendered the midi track and then aligned the audio with the midi then you can see it is plainly whacked. KC

I get weird delays at times with instrument plug-ins (especially Mach 5). I can make it go away by moving the instantiation to another insert slot (same or different track)

Well I changed a few things all at once which seems to have fixed my problem. I upgraded to 10.3.8, installed the updated MOTU USB driver for the MIDI Time Piece AV. Updating the midi driver made Audio Midi Setup not see my interface anymore, so I was forced to make a new configuration from scratch. This seems to have fixed my midi problems with ProTools... Perhaps my AudioMidi setup configuration had gotten corrupted? Maybe the new MOTU driver helped? Not sure, but it works now.