WD Elements Play: Nothing on TV Screen, can't reset or switch it off


I bought the WD Elements Play a week ago, connected it to TV though HDMI and configured it without any problems. Until last night all was OK (watched movies, photos, etc). Since this morning nothing appears on the TV screen and I cannot switch off the device through the remote. I tried unplugging and plugging it again but with no success, neither on HDMI or Composite.

I have access to the device only when connected to the PC via the USB port.

Has anyone had a similar problem or knows a solution ?

Thanks in advance for your help