Originally Posted by stethorn
Could be a dud file on the SD card, the device could be going into overdrive trying to process it, when it can't it just keeps trying.
I don't think so. When the card is inserted, the device processes the books on the card. While doing this, it displays a black processing screen. Once it finishes processing the books, the screen goes away. After that, there is added processing each time the cover is needed. But, bad books on the card shouldn't affect the battery like during sleep.