Anderton
SONAR is extremely reliable in my setup...but it's on a computer that's dedicated to music. I treat it like an appliance, or an MCI 24-track for that matter. I never expected to watch movies on an MCI 
I've certainly used programs that act the way you describe, and X1 wasn't exactly robust. But if someone has consistent, deal-breaker issues when running SONAR, that's not the norm - or this forum would be filled with pitchforks and torches. The solution is out there somewhere...and the last straw is that it's usually some simple thing that if only you had known about it sooner...
+1.
I feel the OP's pain as well; I am certain that anyone who has used any DAW
for more than a week has experienced what he describes.
I have given up trying to blame/narrow down any one thing for the reason Sonar glitches/might glitch/crashes
because the reasons are so numerous that the rabbit whole you end up in precludes any work
getting done(previously stated). If it's mission critical (clients waiting/watching) just do what gets you through...
I have embarrassed myself a few times by stubbornly make trying to make Sonar "do something it did yesterday
how I wanted Sonar to do it" when I
KNEW there were ten work-around's.
Thank GOD that I am finally experienced enough with setting up my system
[read "make all the ****y little hardware and software parts sit together and make nice"]
that almost 90 percent of my most prevalent problems just come down to "pilot error".
I also agree that a discrete, DAW ONLY computer will get you better results faster.
(Imagine never having to worry about virus scans interrupting a rendering, or WIFI
causing wait states at just the wrong time.)
Mel