Hello,
I have the same issue, when I've plugged into a APC powersuply that send a more reliable power the Helios64 was running pretty stable. But now I'm starting to have some disks not turning ON.
Some of the system messages:
[...]
ata2: SATA link down (SStatus 0 SControl 300)
ata2: limiting SATA link speed to 1.5 Gbps
ata3: COMRESET failed (errno=-32)
[...]
the sata 4 and 5 turns ON correctly with 6Gbs