I got the SD card to work. Finally! It turned out that the card had to be formatted using FAT16. I have no idea what format it used before. In any case, the upgrade to ROM 1.22 went successfully.
I want to thank you each and every correspondent in this forum who coached me and offered ideas for the solution of the problem. I am particularly indebted to Tom Scott, who emailed the de-EXE'd files the 49G+ required.
I couldn't have done it on my own. That's one reason why this forum is such a great resource. Thank you all.
-Ernie