Sounds like a bad cable. When you have a defective cable (twisted pairs distributed wrongly) it is possible that it works fine when forced to 100Mbit (by connecting one of the ends to a 100Mbit device), but fails completely when used in a gigabit LAN. The gigabit devices won't fall back to 100Mbit because the cable seems alright. (All 8 wires are connected).
I've also tried several cables, even tried the cable that is on the other working HMNHD.
Another thing that i tried is connected both to the 100Mb switch, they both work fine, but what is diferrent between them is that when i disconnect both on the power button, on the new one the light on the corresponding port (on network switch) stays allways on and on the older one goes off, thus giving the idea that besides the same part number the internal hardware is different!
Both devices are Home Media Network Hard Drive and P/N on both stickers on the back is 31803000 - MHNDHD - Thailand.