Since I'm just finishing adding Win 10 as a clean install, as another boot drive to WIn 7 and XP, I'm just now able to look at this on my machine in WIN 10.
I can duplicate it but it is NOT a version (i.e., 3.66) issue - I can even duplicate it with 3.65 (didn't go back further). And all testing I used both SampleTank 3's VST2 and VST 3 plugs.
I have a 10 part GM song ("Saturday in the Park" - Chicgao) that I've tweaked - part 10 drums are XLN AD2 drums the rest is Sampletank. I had it as ST 2 with Omnisynth 2 (because it was GM tune and I wanted to test Omnisynth 2 - for grins).
When I loaded the IDENTICAL instruments into the same parts in ST 3 using IMPORTED Omnisynth 2 sounds the song froze/crashed Sonar at around 56 seconds (time of crash, loads, sample rates, and other "nuisance parameters" are immaterial, as it turns out).
Trouble shooting I loaded ST3 with instruments on one track at a time and played song beginning to end. IN MY CASE for THIS particular tune/mix, it turns out when I added the requisite Omnisynth 2 Trumpet in ST 3 part 5 it crashed. When I put ONLY that trumpet or any Omnisynth variation of that trumpet in part/track 5 in ST3 and left everything else in ST 2 - it still crashed always at same time/place.
There was NO CPU or memory load indication that would indicate trouble preceding (this song doesn't even begin to tax my system: i7-2600k with 32 GB ram and 12 TB's of high speed server HDD's)
It turns out when I use that trumpet ELSEWHERE no issues (e.g., say in lieu of the piano or bass), when I put other trumpets from other library's (ST3 native, ST2 XL, other add-ons) in that part no issues.
So it seems to be a ST 3 issue with a combination of: certain instrument and sample sets and HOW they get utilized dynamically (FX, macros, etc.) so it will be hard to isolate.
I need to go back and RE-IMPORT Omnisynth 2 just to ensure that instrument and its sample didn’t get corrupted at import.
I will also go over now and try Mixcraft 7 and Reaper and see if I can duplicate this there. Then I will go to IK forum and post.
You are NOT ALONE