I've been using 18G for several weeks now without any problems (well, there it has done a weird "forget the last reading session" once). I am using the included 2gb SD card. I would contact Aluratek. You probably have a faulty device.
Oh, I did have one issue. When using Calibre to load news to my Libre, I put it in the internal memory. When I opened the news folder everything was fine, but when I went back to "ebooks" the SD card folders had disappeared. Going back to the main menu and
then back to "ebooks" fixed it.
