Originally Posted by robko
Sounds like you did a pin reset (paperclip in the hole in the back?). Try a full factory reset (you'll lose your settings etc). I can't remember on the wifi if there is an option to do that in the settings menu or not (check there). If not search the forums for factory reset. Sorry I can't remember what the buttons/sequence is for the wifi.
The problem you are describing sounds like a database corruption issue, so factory reset might be your only choice.
Have done the factory reset too, still nothing.
I've just noticed, on the Kobo Books website, that most books are listed as 'EPUB (DRM free)' and I checked to see that all the books I've bought say that, the only one which doesn't is the one which doesn't work, maybe this could be the issue??