Success! Westerly Pageant's suggestion that I just plug in the USB GPS, wait until it blinks to confirm acquisition and THEN start Seaclear gave me a fix right away, which I confirmed by running up and down the path of my garden to create a track of five knots (tree branches required slowing down).
So reputation has been rendered and now I can start scanning in charts and downloading a horde of U.S. ones to test out the program.
Of course, my boat's hauled now, but I should have the program sussed by spring.
Thanks again. This was severely testing my patience...and of course is the one thing I have never seen mentioned as the source of possible conflict.
I'll be the fellow marching around the park tomorrow staring at my laptop, making sharp turns.