How far off from your last position are you when you reopen the book? I've read of a few instances where someone with a cover with a flap on it would accidentally turn pages a bit while closing the cover (the flap would brush against the screen barely but enough to flip pages).
I've never once had that happen on my Glo HD, even on the rare occasions that I turn it off. I just about always put it to sleep and not turn it off though. Have you tried just letting it sleep instead of doing full shut downs or is there a reason you prefer shutting down? It's a minimal battery drain when in sleep mode, and waiting for any reader to start back up again always drives me nuts
. Sleep means you begin reading instantly when you open the cover.