Yes, sorry, I meant autosave. I thought it would be automatically ticked to "on" but it wasn't.
 
To CakeAlexS, great picture, and here's the answers.
The items listed below in my signature line are current
Results of chkdsk were fine and a screenshot is attached.
I ran driver boost and it said all drivers are up to date.
The sound interface drivers and firmware are current from Focusrite/Novation
I defrag nightly (I know, that's too often, but I like to have it nice and clean).
I couldn't find anything relevant in the Event Viewer, but perhaps I am looking in the wrong place.
 
Thanks for your help. I just had another crash. I had inserted three soft synths with no problem, but the 4th caused it to go groaning into the night.

@the loneliest coltrane, (kidding - couldn't resist).
 
This is from your earlier post: "I completely uninstalled Sonar, reinstalled it as the administrator, and now I can at least open the program."
 
So, please explain to me how exactly you did the uninstall of Sonar.  I just want to make sure you got rid of the registry keys and the hidden folder data.
 
Bob Bone
 

No screenshot for chkdsk but we shall take it for granted :)
 
> I defrag nightly
As you say, way too often! I doubt it will be of any benefit whatsoever, once a month (or after you install lots of software or updates) I suggest minimum unless you fancy a hard drive replacement :
 
Please go back and look at the event viewer, click on custom views -> Administrative Events. Right click on an error with a red icon, Copy -> Copy Details as text and paste here. No need to post duplicate errors.
 
and +1 what Bob says....

robert_e_bone
@the loneliest coltrane, (kidding - couldn't resist).
 

Shouldn't that be 'the loneliest coal train'? 
 
Regarding the issue, my only thought is to run Memtest (http://hcidesign.com/memtest/). The one time I experienced weird stability problems like this was when a RAM module went bad. It hit right after a Windows update, so I chased that wild goose for almost a week before I finally got wise and ran Memtest.
 
 

Something else to keep in mind are development cycles. Even though Cakewalk will likely attempt to test each new Beta version on each version of Windows, they will probably focus primarily on the latest patches and updates. They will not focus as much on testing older versions of Sonar with newer versions of Windows or the latest Windows updates, and certainly without regard to the latest trends in viruses, etc. So, for example, let's say your anti-virus program downloads a new signature database update, then, somehow renders a .dll file a risk, you may allow it to remove or quarantine that file without knowing what the file is for.
 
NOTE: Some Trojan viruses also may replace known good files with a bad one. This even happens with known good patches and software installs from let's say, a 3rd-party plug-in developer (virus developer writes a piece of code, hacks into the 3rd-party plug-in's website and secretly adds their own virus to known good--and trusted code). This happens more often than you might think.
 
So, when new trends in the market occur (good or bad), the older software (X2a) will likely not be tested to survive those trends or patches/updates. Re-install is a probable solution.
 
So, as convoluted as my post here can be, the reality is, that file may have been wiped by your anti-virus software, or became corrupted. In either case, try re-installing Sonar first. If that doesn't fix, try restoring your machine to an earlier time, then reinstall Sonar.