Do you use Lasso's load balancing features, or are you just using it as a process monitor?

Both I've already adjusted Sonar cpu priority to "Above Normal" & I/O Priority to "High" RAM is not an issue and have removed affinity for processor 18 which by default windows appears to start initial load. Ticket has now been raised with Nvidia as I have same issue with AKAI VIP. 1st solution to decouple SLI has made no difference.

Just a (perhaps unrelated) thought...once upon a time, back when I was running a 2-core Pentium and often pushing it to its limits, I was in the habit of boosting SONAR's priority. But then Noel posted an opinion suggesting that MMCSS made this unnecessary and that it could even be detrimental. Noel is quite the expert when it comes to CPU optimization under Windows, having put a lot of work into mostly-invisible tweaks such as priority inversion detection and thread balancing, so I trust his advice.

I  wouldn't want to disagree with Noel and he is probably right, but at the moment just trying to diagnose issue so want to rule out any cpu or I/O throttling going on in background.
Will almost certainly reset them back to normal assuming I get confirmation of a NVidia driver issue. As I also am experiencing a slightly subtler effect with Excel have been adjusting its performance.
Certainly going for bitsum high availability has no effect on SPLAT but does help in gaming.

If this is a system you put together I hope you did the typical burn-in/memory/hw level tests before putting it into production.  
We had a user with some random troubles that came down to bad memory.  Memory tests failed and it was a very powerful system but with off brand RAM.
 
Keith

No it's a Dell built system.

Latest update from NVIDIA:
Please change the following settings in the NVIDIA Control Panel Global Settings under "Manage 3D Settings”:
• Change the 'Power Management Mode' to 'Prefer Maximum Performance'.
Also try changing the below mentioned settings
- Please try changing the performance mode of all the applications. Below are the instructions for the same.
- Open NVIDIA Control Panel --> Manage 3D settings.
- Go to Program Settings tab.
- Add the .exe file of each application by clicking on Add button.
- In the setting window, change the 'Power Management Mode' to 'Prefer Maximum Performance'.
- Click on Save and restart the Computer.
- Run the program and check.

What I've found is no matter what you do on your PC, always run some benchmarks, stress test before you even start to do anything serious. If I ever get the funds and the time to build myself that near-silent SSD and NVRAM based PC with passive cooling, I'll still do that.
 

I have now run a series of identical tests on the SPLAT over a period of time. Each time SPLAT is closed after 15 minutes and changes not saved.
PC on for less than an hour no issues.
2 hours later observing the odd stutter in the graphics.
1 hour later significant delays occur up to 3 minutes to respond to a click on screen, then a period of no freezing and then freezing again. Now impossible to drag objects on screen.
1 hour later only managed to get the app to start playback of a track before complete graphics froze, track still playing. In fact only way out was to terminate SPLAT from task manager.
In all the above there was spare cpu on all processors (19 as 18 had affinity removed), no evidence of additional or forced paging, Total RAM around 10%  SPLAT holding around 7.5GB committed memory. SPLAT under the hood graphics appeared still to be working as expected. i.e Track still playing quite happily
As this is definitely not a SONAR issue so now having to fail over to back-up PC which means as keyboards are 6 feet away an issue but thanks to Craig’s article have purchased a Dragonfly to assist in recording etc.
If I ever get a resolution will update thread again

Keith Albright [Cakewalk]
If this is a system you put together I hope you did the typical burn-in/memory/hw level tests before putting it into production.  
We had a user with some random troubles that came down to bad memory.  Memory tests failed and it was a very powerful system but with off brand RAM.
 
Keith

I made the same mistake once myself. built a high end system and tried to cut corners buying mid grade RAM.
It was the root of all evil. Couldn't figure out where my issue was coming from until I did a mem test.
Swapped it out with high end Corsair and haven't had an issue since (almost 2 years now).