I've attempted a reset by pressing the reset button holding the power button until it resets but it makes no difference.
The problem is, that it has been showing me a loading screen for the last couple of hours. It says "Loading..." at the bottom, I can see the battery indicator (full) bottom left. Middle of the screen I can see a circle with two arrows which are turning (slowly).
I can see the home menu behind these, but it looks greyed out and I can't make any selections anyway. None of the buttons respond.
I have left it like this for an hour at one stage, but it never fully boots.
When I connect it to a computer, the prs300 shows the usb screen and I can browse the device from my laptop, but once disconnected I am straight back to "Loading" again.