Got the promised follow-up email today from Kobo about my original credit card; Customer service says the problem with Worldpay and my paticular credit card has been resolved and all is well. Went to the website, put my original info back in, and bought a book with no problem. Hooray!
Thanks to all who responded for their ideas, suggestions, and just plain moral support.
I think I just got lucky with the last person who received my complaint at Kobo as I finally got an answer that made sense from someone who followed up on the problem. I hope everyone else here can have equal sucess with less hassle.
Now, back to reading...
Plumadona