Any help with this would be most appreciated.....the player has just finished charging via the pc and the cable removed, however, although there is obviously power (blue light illuminated) there is nothing at all on the screen and no sound

Have you re-booted it?. By sticking a paper clip into the small hole at the bottom on the left hand side. This will re set the player and hiopefully sort out any problems.
Personally I always charge mine from adapter, as it seems to take longer from the PC. And the one time I did use the PC I think IIRC I had to re-boot as it caused a problem.

cheers, problem sorted!