I posted this a few hours ago and my post seems to be gone.  If it's still there, let me know so I can delete this...
 
Yesterday a friend listened to a song I started and then quit working on in July. He made some suggestions that I thought were good, so I decided I’d put some more work into it.  When I loaded it in 32-bit Sonar (because I used MusicLab’s Slicy Drummer and Fill-in Drummer for the drum track), it crashed Sonar.  I’ve been on a crazy trial and error mission for the past 24 hours to figure out what’s going on.  Here are some facts:
 

1. At first (about 15 times or so), I could load it with no problem in 64-bit Sonar – but with the MusicLab MIDI plugins non-functional, of course.  Since then, I’ve been able to load the last July track occasionally in 64-bit Sonar and once in 32-bit, though I’ve tried hundreds of times.  I have restored it from online backup (late July backup date) multiple times.
2. Besides crashing Sonar, I have had three BSODs while working on this.
3. I have also had Sonar tell me three times while working with the project that I have no physical sound device matching any installed drivers on my computer, though only Sonar failed to find the sound card (M-Audio Delta Audiophile), while WMP and FL Studio had no problem.  I tried re-installing the drivers, but the fix turned out to be switching Sonar to WMD and then back to ASIO.  In fact, a saved version from that fix actually loaded once in 32-bit Sonar, even though it contained NI Replika (see below).
4. By loading the project in safe mode, I have pretty much isolated the issue to a single audio track with NI’s Replika as FX on the track.  I created and saved a version from the safe mode load where I deleted the audio track, and also one where I deleted it and then re-imported it.  As long as I don’t add Replika to the re-imported track, all is fine.  Also, if I load a re-created, saved version of the project that doesn’t have Replika, I can usually, but not always, then add Replika to the track without crashing 64-bit Sonar.  But trying to similarly add Replika in 32-bit Sonar to this particular track ALWAYS crashes it.
5. If I try in 32-bit Sonar to load a version where I successfully added Replika in 64-bit Sonar and saved it, it crashes 32-bit Sonar. Even though the project is not re-saved, since Sonar has crashed without the opportunity to save, I cannot open the project again in either 32-bit or 64-bit Sonar without crashing.  Any version that worked in 64-bit Sonar but then crashed in either 64-bit or 32-bit Sonar will no longer open in 64-bit Sonar even though it has not been re-saved upon crashing.
6. I CAN use Replika on other tracks in 32-bit Sonar, so Replika is “working,” Nevertheless, I have tried uninstalling and reinstalling Replika, but that made no difference.
7. Looking at Windows Application and System log in event viewer, I often see a C0000005 error.  Faulting modules are always SONARPLT.EXE and sometime also TTSRES.DLL.
8. I have unplugged USB devices, etc. One time I got it to run in 32-bit after unplugging the cable from my GAIA SH-01 (which happens to be the synth that the audio for the “bad track” comes form), but closing and then trying to re-open crashed it again.
9. I have looked at new software that’s been added to my system since July.  I upgraded Acronis from 2016 to 2018 yesterday before starting on all of this, so I uninstalled Acronis and re-installed 2016.  No help.
10. I tried rolling back SPLAT to July.  No help.

 
What am I missing???

I don't think your missing anything. Your just seeing what happens when you try and use 32 bit in a 64 bit system. 
 
Your best bet is to scrap all plug ins and VST's that are 32 bit and replace them with 64 bit versions. I just ran into this a few weeks ago when trying to play old projects that still had just 1 32 plug in. They where crashing but only sometimes. I removed that one VST ( mr Tramp) and since then no more crashs. 
 
I know it's a lot of work to change drum VST's but for me AD2 always sounds 100% better once I dial it in. 

I have thought many times that maybe I need to get with the program and wean myself off of 32-bit Sonar.  But even if I did, I would leave it installed so that I could go back to old projects that I never finished.  More than 90% of my projects use Musiclab MIDI plugins and I'd at least want them to open with the plugins intact.  I have had really no problems until now using 32-bit and going back and forth between 32-bit and 64-bit.  So I'm  still looking for a suggestion for how to fix this.

The biggest difference between 32 and 64 bit performance is that 64-bit can use all of your physical memory while the 32 bit is limited to less than 4GB of memory.  All other things being equal, you will generally see more efficient performance with 64-bit.
 
If the project is memory-intensive, then that may be something to look at.

Does anyone know if there is a way to exclude 32 bit plugins from showing up in 64 bit Platinum? I have tried to remove their folders in the plugin manager but, they will not go away.

rodreb
Does anyone know if there is a way to exclude 32 bit plugins from showing up in 64 bit Platinum? I have tried to remove their folders in the plugin manager but, they will not go away.

Not sure this would fix it, but did you re-scan after removing the folders?

smoddelm: Yes. Re scanned, closed and re opened.

Use Preferences > File > VST Settings to set up the scan path and run the Reset from there. Make sure the 32bit plug-ins left over are not in the 64bit scan path. Cakewalk puts some 32bit plug-ins in the 64bit scan path. For those plug-ins either move them out of the scan path or exclude them using the Plug-in Manager.

Thanks, scook. I'll try that.