Problem solved, Operator error!
Distracted myself by looking at a symptom when the real problem was further upstream!
I even carefully compared it to the stitching of my Windsor B, to see what the WB was doing that the NH wasn't.
Here are some symptom closeups...
see the loop forming topside...
[ATTACH=CONFIG]459933[/ATTACH]
[ATTACH=CONFIG]459934[/ATTACH]
So the needle would occasionally pierce the loop, and break the thread... and the problem was actually...the take up lever wasn't moving. Because when I reassembled the needle bar assy, I neglected to re-engage it. Duhh. And now it's better, much better. Now I need to get a little more traction out of the drive wheel, but that's easier.
I'll post a photo of the culprit, once I get my Netbook to let loose of the SD card so I can put it back in the camera. Sometimes problems are simpler than we think. Good news is, I now have 2 extra shuttles, (new) because the old one is working fine. Oh, I did squeeze down some of the free play around the shuttle, thinking it might have been that, and had to back it back out a hair. I love puzzles!