I have just recieved my WD TV Live box and as soon as I had the device in my hands I plugged it into my TV and logged it on to the internet - no problems there!
It did automatically update the firmware to the newest version and wupti, ready to enjoy all my great movies from my external USB-drive. But when I plug the USB into the device (I have tried both USB-ports), nothings seems to happen. I have tested with a USB-stick/pin and it worked fine with no problems.
I have a WD Elements Desktop 1.5 TB disc (ntfs formatted) which works great on both PC and mac.