Sometimes the WD Live Hub does not see a usb drive connected to it when I browse in folder view. The strange thing is that I can still the drive and play the files on the drive over the network on my computer and via a networked WDLive unit.
This has happened on both USB1 and USB2, though not on the internal drive.
This also sometimes happens with an individual directory: The directory just disappears when I browse for it in folder view on the WDHUB, but I can still see it and the files in it over the network. This has happened on the internal hard drive.
The only way to correct this seems to be to unplug the power to the WDHUB, and plug back in.
This does seem to have started with the latest (3/8/2011) firmware.