Everyone,
 
Thanks for all of the helpful information.  Apologies for not getting back sooner.  Unfortunately, real life beckons sometimes (I wish music production was my "real life").
 
So, I did spend most of the day Saturday tracking, and some mixing yesterday, without a hiccup.  New projects seem fine.  Old projects (like a year or more old) pull up fine as well.
 
I'm starting to think it's related to a new VSTi, EZKeys, which I had recently installed and used on a project, and that's the project that gives me the runtime error, which has turned into the only source of crashes in the past couple of days.  I'm going to see if I can duplicate the error with a new project with EZKeys in it and, if so, reinstall it, take the usual measures, but X3 seems ok for now, I think.
 
So I probably owe Cake an apology.
 
I did just update the Lynx drivers and firmware, I believe earlier this month, but I'll double check.
 
Yes, the Lynx and Sonar sample rates match.  The Lynx will occasionally want to run at 48, in which case I can't do anything until I go into the Lynx software and change it back to 44.1.
 
As for overclocking, my instincts told me it could be the problem, except that it hasn't posed any problems in the past and my friends at ADK informed me that it was absolutely fine in my setup - in fact they did the overclocking.  This was not always the case - only a couple of years ago they strongly recommended against overclocking.  So things/technology changes, I guess.  I do get into some pretty low buffers recording, which is cool, i.e., 64 is no problem, 32 ever works most of the time.
 
And no 32-bit plugs in use on that project.  Overall, very weird.  Spirits in the machine.  You know how sometimes you have a day of issues, and then they seem to disappear?  No?  Maybe it's just me...
 
In other news, before all this, I had switched to this machine as my main DAW, so installed a new video card, two UAD Quad cards, and a TI chipset FW card.  Of course, most of my music software thought this was a new install, and I had to go and re-authorize most of my plugs and synths and/or re-install them (missing presets, for example).
 
Even X3 was affected, as my custom plugin menu was nowhere to be found, the one I spent hours putting together.  Oh well, re-doing it gave me an opportunity to look at all of the expensive plugins I never use, LOL.
 
As my wife says, do you really NEED more?  Well, it's just a new version...  and I don't really NEED it...  but...
 
Thanks again, especially Mr. Bone, for your detailed assistance.

Treefight
So I probably owe Cake an apology.

Very nice. SONAR tends to be everyone's whipping boy, but few are classy enough to follow up with the OP like this.
 
FWIW, overclocking is something you may want to revisit at some point. The thermal issues caused by that are not instantaneous and cause degradation over time. Especially this day in age, there are very few things that will tax a CPU (to 100%), and is usually for shorter durations, so the thermal spikes are not persistent (video processing and encryption algorithms are two big ones that will). Most of the CPU's life is spent at low CPU load, so placing a higher voltage on it is not increasing its life expectancy (or adding benefit).

Chris thanks for the update.

Hi, I've just got X3 installed like it comes in the 4 parts.
 
Do I need to download and install all the updates or just skip to E?
 
Or do I want to install E? Seeing a lot of post about problems with E.
 
Thanks

Install E. I don't see any posts about E being a problem. I know that lots of bugs were fixed in E. 

+1 Many of the posts are closure to bugs reported in d that were fixed in e. Sorry for the confusion.

Everything starts with an E.