I was not sure where to post this so I put it here.
 
I updated my video drivers last night and have not had another crash on closing my projects.
 
The Problem report was CWBRN-49296.
 
I am running an NVidia GeForce GTX 750 driving an Acer 27" monitor and a 49" LG UHD TV at 3840x2160.
 
Before I Installed the new drivers some dropdown menus would flicker in Sonar.
 
Now all is good...

Hello Bluegrasser. Which drivers are you using? I'm having the same issue. I've tried the most recent drivers and I'm getting the same results. Grrr!!

I have a 4 GB Windforce GTX 750 Ti by Gigabyte, and am running v364.72 of the driver and PhysX. If you are on that version, did you install all of the other bits, or just the driver and PhysX? If everything, try getting rid of all of the other apps and check again. You don't need all of the 3D and gaming code mucking things up.
 
And remember to go back into the Device Manager and disable the HDMI audio driver that keeps getting reenabled after each driver update.
 
For what it's worth, NVidia have just uploaded a new stable release, v365.10. Downloaded just now. Installation next.
 
EDIT: Restarted SPlat. No issues noticed (of course, I didn't have any before). Hope the new version works for you.

I only installed the driver (v364.72) not the other bits. But I will try the newest driver. TheMaartian, thanks so much for all the info and driver update. 

I just noticed in the OP that the poster is running his display at 3840 x 2160. FWIW, I'm running at the standard resolution of 1920 x 1080. I don't know if that makes a difference, or not.

I'm on Version 358.91 of the NVidia Drivers.
 
I just saw the problem reports forum so I will repost my original post there.