Thanks havplenty and shnnn. After I posted this question, in the back of my mind I was thinking I needed to go put the question somewhere more appropriate - but then I didn't want to double-post. And I threaded/unthreaded/rethreaded.
I did post my question over in the Vintage machines folder. And the answer was stunningly simple. I'll give it here since I already posted the question here. I was running through only 1 layer of fabric, not really enough for the lockstitch to lock. And I thought, "Duh!!! When do I ever run only 1 piece of fabric through (other than a small fabric leader)?" It wouldn't be sewing if there were not 2 pieces of fabric.
So I ran 2 pieces through, made a couple of small adjustments and voila! Looks like a great stitch.
I am so happy - and she is so pretty! I have to come up with a name for her...[ATTACH=CONFIG]306320[/ATTACH]