Unplug Hub for few minutes, start again go to Video for example only one partition will appear press red button than use other media you will all data on the USB
I had to format my USB HDD … in the end I decided there must be some quirk with the format, it was reporting FAT32 but it had never been formatted since it was manufactured. I deleted the partition, re-created it and formatted it with FAT32 using GParted on a Linux machine and then the WDTV could read it fine. Seems the current firmware might be a bit fussy about partition format.