Kev, I wouldn't bother with a reformat or reload OS just yet at all.
Mine does that from time to time, seemed to happen more when I first got it. Wouldn't turn on, as if the on button wasn't responding to my pressing it (or holding it). Just popped off the back of the case, pulled the battery so that it lost contact, slid it in and it powered up itself.
It happens! Lesson learned, try the battery trick
I just dropped my JB3 off my desk and onto the basement floor
On accident, not trying the "D8 5 foot test"
Seems okay, plays fine--but I'm still a little shaded out!