What version of the firmware are you using, njok? Have you tried "upgrading" it, even if you're running the latest?
Unless the hardware is damaged, I'm guessing the malfunction could be a software thing. I'd try the update, anyway (download the .hex file from the iRiver website and copy it onto the lowest level on your Story, then disconnect the USB and restart the device. It should start the update automatically. Watch the screen for prompts and let it go all the way through the process before rebooting it or switching it off.
See if that helps, anyway. It won't delete any of your books.