I discovered I did indeed have a dual installation of one of the libraries, and the software was picking up the old one. I've fixed it (not happy, as I've got a link across from /usr/lib to /usr/local/lib - but hey! it works).
And then of course, I ran into the QtWeb issue which is discussed on another thread. Suffice it to say that I downloaded a package from the Intrepid repository, and Calibre finally sprang into life!
And I'm very impressed with the software so far.
I have to say it's a pleasure to get such an efficient response from the writer of the software. My congratulations to you on a fine piece of work, and I'll be making a small donation to your site very soon.