Memory card storage limitations (just in case anyone else is as dumb as me...)
If anyone else has invested in a 2GB card, tried to transfer more than about a hundred files to it using libprs500 and got an error message what they do not understand, the way round that i've found is to use a card reader and create folders on the card. Put about a hundred files in each folder and it works. Of course, the Reader takes about a hundred years to work through the card when booting up and shows all the files at once, so navigating through to the book you want is a page-by-page job, but then, if you didn't want that many files on the Reader at once, why get that big a card?
(i know this is probably thuddingly obvious to all the aficionadoes on here, but i couldn't find a thread on it so this is a PSA to all the beginners like me.)