I've had various version of sonar, x3 now. I've come to accept that it will crash occasionally, but lately it's been so bad I can barely use the program.
 
When I start to record, more than half the time X3 will crash. I thought it was only if I had a punch region enabled, but now I don't think so. A few minutes ago it crashed on playback, rather than record. 
 
I've made no changes to my system. I'm using the same 2 interfaces I've had for a while, namely a Focusrite firewire interface and a Line 6 Helix. It will crash with either of them.
 
I downloaded the platinum trial to see if it was any better, but that crashes too. I just ran memory, disk, and cpu diagnostics on my box, they all passed. I'm not sure what to try next.
 
Does someone here have any suggestions?

What is the nature of the crash? Is it a freeze, the program quits, it sends out a dump report, or...? What OS are you using, 32- or 64-bit? The reason why I ask is that while you may not have made any changes, if you have Windows updates or driver updates done automatically, something could have changed. 
 
You really shouldn't be having constant crashes, I can't remember the last time I had a crash with Platinum so if it happens with Platinum and X3, that might help point to whatever is causing the problem.
 
Also FWIW when something goes bad "all of a sudden" I get very nervous that it might be a hardware issue.

Wow, that was fast! The program crashes and produces a dump, I've submitted several of them as problem reports. I'm on Windows 10 Pro 64 bit.

I checked for restore points that might indicate whether there was an update, the only change I can confirm is that the new Melodyne got installed. My project doesn't use that.

As I said, I ran diagnostics on disk, cpu, and ram, all passed. I'm considering a clean re-install of the OS.

I found X3 and win10 to not be very happy together but havn't had any issues with Splat crashing other than the known issues with Melodyne, but your not using it...
 
Win10 updates are known for 'changing things'. check all your preferences for both PC and SONAR.

Make sure that Win10 updates haven't re-enabled your onboard audio chip and made it the default!
 
Bloody Microsoft 

Win10 pushed an update yesterday - I got home an my Win10 laptop had rebooted and indicated an update was installed.

I have found that if I open comp and get to the desktop, I will sometimes engage cake to quickly and I find that win10 must still be loading other items. Cake takes longer to load and I have noticed that sometimes items are missed or turned off while the two software systems scrambles for resources. Now I let the comp sit for a sec while I make a cup of Java. Return and load cake and I haven't had a problem. Knock on head. Just a thought. I remember reading this on a post awhile back. About letting programs load completely before pushing buttons. You can't start the car in drive.😊

As a person with outdated hardware (see my signature, with some luck I get 2 GB moor soon ), I can confirm that running/stopping Cakewalk products "too fast" can cause problems (had that with X1-3, SPlat and RP). But OP is about crashes when X3 is running.
 
The usual sequence: disable all plug-ins in project, increase ASIO buffers, remove all Control Surfaces plug-ins (especially in case you use Mackie/VS-700). As the last resort, switch to WDM mode on build-in Audio. Once you found not crashing setup, start adding disabled features one by one to identify faulty component.

How long since you've been on Win 10?  Does that time coincide with your issues?

bojackey
I'm on Windows 10 Pro 64 bit.

The think I absolutely despise about Win10 is the forced updates.  I have now had 4 occasions where forced Windows updates have wrecked a computer or cause apps to fail.  Fortunately for me, none of these have been on the machine running Sonar, so this may be completely irrelevant to your situation.
 
The most recent problem happened in December and my computer would just lock up periodically.  I could run applications that were already launched, but I could not launch any new ones, and I could not do an orderly shutdown to reboot.  I did roll back the updates twice, but in a few days, Windows would just install that garbage again.
 
Then there was a package of updates installed a couple of days ago.  Now it seems like the system is stable again.
 
This is probably not your problem, as it appears you have a more specific issue.  But as a general bit of guidance, if one has Win 10 Pro version, it is possible to instruct Windows to delay any non-emergency patches.  Highly recommended.