Hello Alex.  Yes, over the past year and a half, I have written about this problem a couple of times, tried many different fixes, all without resolving the problem.  The additional piece of info this time around is that I get no crashes/freezes when using Reaper, and this suggests to me that the computer hardware is all solid and not the source of the crashes (something I didn't know when I wrote the previous post).
 
As to RE Bone's point (2), I can say that yes, Sonar will load and run both with the audio interface connected and not connected.  I have not tried to use Sonar for an extended period of time without the audio interface (to see if I still get crashes), because this takes a great deal of time away from audio production.
 
As for RE Bone's point (1), I can easily instruct Windows to send Windows sounds to audio output I am not using.  I will report back in a week or so with whether I am still getting crashes.
 
 

Hello Cactus Music.  Thank you for your reply.
 
You raise for me an important point.  I paid $150 dollars to upgrade Sonar 8.5 to x2 (I've been a CW user since 1998, and over the years have upgraded 8-10 times - I have a lot invested in CW!), and what I got is software that fails repeatedly.  IMO, having paid for it, CW owes me a working copy of software.
 
Should I now spend another $150 to get Sonar x3?  Then I would have spent $300 to get a working upgrade - and there is no guarantee that x3 will work for me any better than x2.
 
If x3 will resolve this problem, then I feel CW should refund to me the price of x2.
 
(Think about it for a minute: as a customer, do you really want to see a software company churning out crappy versions of their product as a way to boost sales of the subsequent version?)  

Question for AlexS - you mentioned speed-stepping in your initial response to my post.  I have turned off speed-stepping in the BIOS (which is mentioned as an important tweak for audio computers on some web-sites i.e Sweetwater, etc).
 
Is speed-stepping something different from Core parking, or are they the same thing?   I have to find out more about this.

X2 was released by Cakewalk owned by a different company, Roland, so you would have to take up your beef with them. They were screwing up with X1 and 2 and I'm sorry you took the bait. 8.5 was rock solid and those of us who stayed with it saved a bundle of money.  
Cakewalk is now owned by Gibson and they have made huge improvements IMHO. 
 
Like I said, try the demo then you'll know for sure.
 
The only other thing I could suggest is that Mackie's drivers might not ever work smoothly with any version of Sonar, You might want to post on the Hardware forum and ask: 
 
Any x3 users with a Mackie Onyx 1604 w/ firewire ? 
On this forum your threads disappear to page 2 in a few hours because of the over abundance of threads about the new release.  so it sucks. Real questions are not all getting answered right now. So the Hardware forum is a good alternative. 
 
I'm sure there are other Mackie Onyx users here and it would be great if you could get feedback from them. I really doubt it's your actual computer, you sound like you have looked into the usual fixes.
Mackie makes good stuff, and Sonar is a great DAW again since X3e, so don't give up yet.  

If you've disabled speedstep then you've also effectively disabled core parking I believe for all OS's installed on your machine

Yesh - as far as that second point I had posted earlier, about testing without the fire wire audio interface card installed, I was only suggesting trying that for a test - not to suggest that you just stop using that interface.  I was just trying to understand if it made any difference with regard to your issues.
 
For my first point - I have experienced issues at times in the past, when having multiple applications trying to get control of an ASIO driver, such as Sonar as well as Windows.
 
Soooo, I was suggesting you try setting the Windows Default Audio Device to something other than the ASIO drivers of the audio interface.  I think this may well clear things up for you - it is certainly worth giving it some testing time, which I do understand you are willing to try.  I look forward to seeing how that turns out.
 
Bob Bone
 

Hello.  Question for Mr. Bone:
 
So in Win 7 -> Control Panel -> Sounds, I see 4 tabs: Recording, Playback, Sounds, and Communication.  Under the "Sounds", I have it set to "No Sounds" and have unchecked the box that says "Play sounds when opening Windows".
 
Under the "Playback" and "Recording" tabs, there are a number of devices listed: the Mackie interface, a SPDIF input and output that is native to the MOBO, and an analog output that is native to the MOBO. 
 
Currently, under both the "Playback" and "Recording" tabs, I have the Mackie device selected as the default device.  If I understand you correctly, you are suggesting that I should select one of the other devices as the default device.
 
This is an easy change to make and I will try it and report back.  Thanks for the suggestion.

Hello Cactus,  thanks for your thoughts.
 
Yeah, baby: Sonar 8.5 under Win XP was rock solid for me.  I used the same Mackie mixer with firewire interface and never had a problem - doing 8 hour recording sessions with 10-16 inputs into the computer without a single click or pop.  What a rock!
 
And I got worried about Win XP getting old and also wanted to build a new computer with greater RAM.  So I bought Win 7 and upgraded to Sonar x2.  (In fairness, with my current set-up, I am also able to do hour-long sessions with many recording inputs - and sometimes, randomly, these sessions are interrupted when the computer freezes, and I lose everything since the last save.  I literally hit Ctrl-S after doing anything in x2 now.)
 
I posted the question here because it seems like the right place for questions about Sonar X series software.
 
 

Has been written many times I really think you should try an external display adapter at least after you've tried everything else. You can pick 'em up cheap...

I would get away from the way of thinking that it is Sonar/ that other apps are more reliable although the perception is totally understandable. Most people are not experiencing your issue with Sonar. It is definately drivers/hardware/under the bonnet OS issue.

Anyway plenty of ideas here good luck...

Hello.  I appreciate the suggestion AlexS.
 
I hesitate because it is a shot in the dark.  And I do not have infinite resources of money and time to tame this problem.  I have already bought an additional firewire card and additional RAM modules - on reasonable suggestions such as yours -  and none of those things fixed the crashes/freezes.  It was money and time wasted - and I need my money and time to do productive things.
 
Do you have examples from other users who have computers similar to mine who experienced similar problems that were actually resolved by installing a third-party VGA card?  Any community forum posts to that effect?