when I load an instance of Kontakt, there's a single note that wont playback.  I triggered it when recording (sounded fine) but when I go to play it back it omits that single note!  Any ideas?

Is it a note at an extreme end of the keyboard.  Maybe that note is assigned to a keyswitch function for a given patch.

Have you got anything particular loaded in Kontakt? What version of Kontakt are you using? I use Kontakt a lot and haven't noticed a problem.

There should be a "Weird Sonar Behavior" thread...
I have the weird is stuff happen daily!
AND what makes it worse is that I have to track down the problem and I always start at the mic and go to the computer because it worked the day before! So an hour or two lost when I could have rebooted my system and the problem is gone!
 
last week, and actually all I was doing was testing some cheap new mic cables from India.
So if it isn't working that's what I'm looking cable issues... hit record and I get this horrible hum...
New Cables not good! I put back the old ones... and still now the hum... a few hours to trace then I'm in SPlat...
mess around with some plugins try this and that... at this point I have this hum on record and mono on your side. so I put on headphone... yup! only the left side is now working... so I click on the out buss to 2nd audio out set to shut it off... when I did that... looped internal feedback hit my ears! They are still screaming! But after that everything was fine! Well today I had the only left side playing as recording / monitoring playback. but it magically went way when I clicked the buss off and on... 
 

Try raising the MIDI Prepare Using Buffer to 500ms in preferences if it's at the current default of 250ms, or higher if it's already at 500. This is the most common cause of dropped MIDI notes.

brundlefly
Try raising the MIDI Prepare Using Buffer to 500ms in preferences if it's at the current default of 250ms, or higher if it's already at 500. This is the most common cause of dropped MIDI notes.

Didn't work.  I checked everything.  It's just not triggering those midi notes.

is it this..?    https://www.youtube.com/watch?v=QFyhneelbqI

nope.  Really infuriating.  I suppose I could try re-recording.  That's annoying.

Is the errant note assigned to a Midi channel which Kontakt is expecting?
Is it at a reasonable velocity?
Does this note sound if you click the corresponding note on the keyboard to the left inside the PRV?

Yes to both.  The notes are playing on the kontakt keyboard...it could be kontakt.  But I always seem to have problemo's with kontakt in sonar.  why is that?