After the latest update I've noticed that some of my old instrument track presets (for Kontakt and Maschine) are making my PC really really slow. Saving takes many seconds etc. I remember similar situation making some instrument track presets using Massive from last summer. Replacing the synth instance solves this but it's a bit frustrating that I basically can't trust my "go to presets".
 
Has anyone else noticed this kind of behavior? The same happens on my laptop and desktop.

I would try purging your PC using Ccleaner first.
And im not sure about you but sometimes I leave my pc on for extended amounts at a time.
So be sure to do a reboot. This will clear out anything that may be corrupt in your RAM.

I appreciate the input but that cant be the case because this is happening on two different computers after the latest update.

Wish I knew what to tell you, My kontakt presets are working here and some of the presets I have date back to X1.
(for Ric bass, Slate drums, Studio Drummer, exc)

There is something with the track presets that doesn't seem right. Just tried to transfer a nice Omnisphere synth sound from a project to another and it seems to get muted for short irregular times. Also the input echo button doesn't lit from track view but works from console view.

something is not right with your set up man.
I just fired up sonar 2 seconds ago and input echo works in track view and console view.
 
I also just copied about 20 of the oldest presets I could find on a storage disk an imported them.
Some as old as 8.5 for Kontakt. no problem at all.
 
weather or not you take my advise about  Ccleaner is totally up to you.
probably wont solve your issue but it cant hurt either.
Something is either corrupt or a reg setting is bad. 

JoeHans
There is something with the track presets that doesn't seem right. Just tried to transfer a nice Omnisphere synth sound from a project to another and it seems to get muted for short irregular times. Also the input echo button doesn't lit from track view but works from console view.

That sounds like something is operating in Demo mode

Bristol_Jonesey

JoeHans
There is something with the track presets that doesn't seem right. Just tried to transfer a nice Omnisphere synth sound from a project to another and it seems to get muted for short irregular times. Also the input echo button doesn't lit from track view but works from console view.

That sounds like something is operating in Demo mode

good point Sir Jonesey,
I didn't even think of that. could be Kontakt or your other synth in demo mode / ala-Drop out demo syndrome.

The muting happened for Omnisphere instance. I checked and there is no demo for Omnisphere so it can't be that either. :/ The problems occur only with some track presets.