Same problem here. And i think that the trouble is not in the power. Because of you do a master reset of WDTV, it detect HDD only once and can read a files, but after power off/on - there are no hard drive. Again master reset and it works.
more over, 25H2P has splitted to 2 ports USB cable, iv’e used additional 5v 500a power source for it and no use
there are probably some king of a bug in firmware, my device has latest 1.06.15
