[sarahsbloke]

You need to get it so the time and battery status are showing

Then press the "Nook" button in the centre of the black strip betwen e-ink and LCD displays.
That should fix it.

When using appmanager to exit you also press the "Nook" button.
It didn't lock up, you just didn't know how to exit.

I usually then use taskmanager to close any unwanted running apps.

If in trouble, always try the "Nook" button first.