Well, the long travail comes to an end at last. And, I must say, the StarForce guys deserve the credit for pointing the way to the solution, and it looks like it probably turned out not to be their fault after all.
They actually did respond to my e-mail, and asked me to do some things to collect error messages and minidump files to give them some info about the crashes. When I did so, I finally saw an error message that made reference to what looked like an nVidia graphics card driver. That caused me to remember that I was using a beta set of video drivers that I had installed to fix a graphics glitch problem I was having with IL-2/FB/PF, so I installed the latest "official" video card drivers and voila! - SH3 works again!!!!!! (The StarForce guys' later response to the info I'd sent them also indicated that they thought the nVidia drivers were the probable source of the problem - I'm still not crazy about their protection system but gotta give them credit for helping out when they didn't have to)
I can't believe it turned out to be that simple, but I'm loving it anyway - loaded up GWX with my personal tweaks last night, and it looks awesome so far (just barely pulled out of port so far, but still - AWESOME!)
Only thing I can figure was that I never actually tried running my fresh install on this machine - I copied in my old tweaked GW1.0x install right on top of it before I ever ran it, and my opening sequence may have been modded/tweaked in that install in some way that allowed it to work with those beta drivers somehow, whereas something about the stock game intro sequence caused some hiccup with those beta drivers. Whatever it was, I'm glad it's over and I can get my Kaleun back out to sea
Thanks to all you folks who offered help and suggestions, here and in PMs - this community is the best I've seen since my old IL-2 days for helping out in a pinch - much obliged!
To anybody else having a similar problem - word to the wise - check your video drivers !