Hi there - I run a maintenance current Windows 8.1 desktop, with 32 GB memory, and multiple TB drives.  Everything is split appropriately, and things run quite smoothly, and everything is VERY stable.
 
I couple of months ago, I picked up a couple of expansion packs for Kontakt 5, including the Aria Violinist, and have been experimenting with it, and have run into some issues.
 
1.  If I simply load up Aria Solo Violin from its presets, into an instance of Kontakt 5, it plays just fine.
2.  If I go into the instrument and make small modifications, like removing the Reverb and making the initial attack a bit quicker, then quite often I can no longer get any sound output from Kontakt, though it is clearly being fed midi data.
3.  If I close that instrument and loaded the original back in, then again it plays back fine.
 
So, it seems like it freaks out when something is edited, and I am wondering if anyone else has experienced these kinds of problems, with the Aria Violinist expansion pack or similar issues with any other soft-synth.
 
I will continue to experiment with it, and if I can figure it out I will post back, but at the moment I am at a loss.
 
Bob Bone