Mixture - I've never formatted an SD card before use, and have three cameras using them, and never had any problem downloading until now. I formatted the new one I have just used to play with via the camera menu, not the computer, and as mentioned, that does now transfer OK.
Dazdaz1 - I connected the camera to the computer with the supplied cable as detailed in the guide - no use. I haven't yet looked at the other options suggested in the guide, that will be my next trick !
Grumpy Old Fart - as above to Dazdaz1.
EEngr - I guess I just took it out, i.e. didn't use the "Safely Remove Hardware " option, but then again the slot isn't a USB slot, but a dedicated SD reader, this is not the second time I have tried to download, I've done it few times since starting, only this last time has proved impossible. The OS is Windows H'eight.
The guy who sold me the new SD card mentioned that he also had one or two SD cards that just refuse to divulge their data after a few successful applications.
Thanks to all for the suggestions, will keep battling and advise - hopefully !
P.s. I was able to transfer the latest photographs off the troublesome card on to an iPad, then e-mail them to my laptop, then Save As in my picture folder, then edit via my photo editing programme ( Picasa ) but this is Sledgehammer and Walnut stuff and shouldn't be necessary, and hasn't been until now.