I've just checked that both dictionaries have content (using the PC version of mobipocket reader).
I've downloaded from mobileread: "GNU Collaborative International Dictionary...", and the "Webster 1913....", and still with the same problems.
What scares me more is that I've just downloaded the Users Guide of the Cybook, from Bookeen's site, and after installing it in the device, I only can see the cover and TOC, but when I advance in reading, clicking on a TOC link or just page after page, no content is showed on the screen. This book, as the others, works perfectly on the computer.
Ohoh!!, more problems that I've expected to have.
Thanks for your help.