First try to reset all logos to none and restart (Power off/on) the Pocketbook.
If this does not solve the problem, try to set it to a default logo (e.g. Bookland) and reboot the Pocketbook.
If this both doesnt fit the problem, push the reset button (On the back of your pocketbook beside the battery) for a short time, i dunno why this is fixing such probs but at me it did work.
If this all doesnt fit the problem, you should do a hard reset.