I have an intermittent issue with MOTU and Sonar.  Sometimes, when I start Sonar and load a project (not play the project) I will get static/crackling on the output on my MOTU 896mk3 Hybrid (and I see it on the output in Sonar).  Usually I can exit Sonar and restart Sonar and load a project (any project) and the static/crackling is gone and never returns for the day.  I've had 3 896mk3 Hybrid's (two new and one refurbished) and they all have done it.  It only happens with Sonar.  I have Studio One 3 and it has never done it with that.  I've tried the MOTU with Windows Media Player, Band in a Box and youtube and it has never done it with that. 
 
I used to have a Roland Octa-Capture and it never did it with that unit.  I have a Tascam 16X08 for backup and it has never done it with that.  Just the MOTU and Sonar.  I'm using the identical, default ASIO setup in Sonar for audio devices, no changes.  I've tried different buffer sample settings for the MOTU and that does not appear to be the issue.  The MOTU person I've been working with has no clue to what could be causing it.

Try a different USB 2 port.

Its been on different USB ports, different USB cables, different buffer sizes.  I tried it with my Laptop about 2 hours ago and it did it the first time I opened Sonar, but never did it again after that.  Another different USB cable was used with the laptop.   
 
All the obvious things have been done.
 
Once it stops doing it, its good for the rest of the day and maybe several days before it does it again.  Its powered off till I need it, but I left it powered on all day yesterday and it only did it twice (first two times I ran Sonar) and never did it again after that.

Strange, indeed.
 
You wouldn't have a firewire port on one of those systems, would you?  Would be interesting to test that driver/connection...

I've got a firewire port but its not a T.I.  Usually anything other than T.I. and there can be problems.

Grasping at straws, it sounds like Sonar is sending something to the card that isn't audio but the interface is trying to play it. Sysex?

Not using any MIDI.  Just "analog" tracks.  And only happens with the MOTU, no other USB recording interface unit.
For the record, I tried it this morning and no clicks.  But that's the way it is, may do it one morning when first tried and not the next.  Has only done it with Sonar, nothing else.
 
 

FWIW, it has not done it this morning.  Powered on my recording rack (and MOTU).  Let everything initialize and then started Sonar and an existing project.  No clicks.  Been on for about an hour and still clean.  But, that's the way it works, may do it one time and not another.  No change in hardware or software, same as it was yesterday when it acted up.

I'd try changing USB cables one more time. I just spent a long time tracking down sparse, random crackling of a Behringer X32 used as audio interface and it turned out that the cable was the troublemaker. USB cables and USB interfaces have a strange relationship - some work out, some don't, some work but not forever ... so in my case even swapping it  for the same brand USB cable fixed it.

Its happened on 3 different USB cables and several different ports on the PC (including front and back USB ports and USB2.0 and 3.0 ports.