Yes Harry, you are right the fonts.cache-1 and the "user" folder had to be deleted. There is a third file in the system folder which had to be left. I can't remember its file name.
I have downloaded all my eBooks from Mobipocket and Fictionwise and everything now seems to be fine on the alternative SD card.
I thought it was a goner but Bookeen gave a fast (and accurate) response.
Otherwise, I am enjoying the Cybook. I was quite amazed at the lightness of it and the leather cover is really great.
Thanks for the welcome.