Just checked my syslog and it's riddled with these error lines:

 

Oct 17 01:01:05 Angband kernel: ata2.00: status: { DRDY }
Oct 17 01:01:05 Angband kernel: ata2: hard resetting link
Oct 17 01:01:14 Angband kernel: ata2: SATA link up 1.5 Gbps (SStatus 113 SControl 310)
Oct 17 01:01:14 Angband kernel: ata2.00: configured for UDMA/33
Oct 17 01:01:14 Angband kernel: ata2: EH complete
Oct 17 01:01:15 Angband kernel: ata2: exception Emask 0x10 SAct 0x0 SErr 0x10200 action 0xe frozen
Oct 17 01:01:15 Angband kernel: ata2: irq_stat 0x00400000, PHY RDY changed
Oct 17 01:01:15 Angband kernel: ata2: SError: { Persist PHYRdyChg }
Oct 17 01:01:15 Angband kernel: ata2: hard resetting link
Oct 17 01:01:23 Angband kernel: ata2: SATA link up 1.5 Gbps (SStatus 113 SControl 310)
Oct 17 01:01:23 Angband kernel: ata2.00: configured for UDMA/33
Oct 17 01:01:23 Angband kernel: ata2: EH complete
Oct 17 01:01:24 Angband kernel: ata2: exception Emask 0x10 SAct 0x0 SErr 0x10200 action 0xe frozen
Oct 17 01:01:24 Angband kernel: ata2: irq_stat 0x00400000, PHY RDY changed
Oct 17 01:01:24 Angband kernel: ata2: SError: { Persist PHYRdyChg }
Oct 17 01:01:24 Angband kernel: ata2: hard resetting link
Oct 17 01:01:32 Angband kernel: ata2: SATA link up 1.5 Gbps (SStatus 113 SControl 310)
Oct 17 01:01:32 Angband kernel: ata2.00: configured for UDMA/33
Oct 17 01:01:32 Angband kernel: ata2: EH complete
Oct 17 01:01:33 Angband kernel: ata2.00: exception Emask 0x10 SAct 0x0 SErr 0x10200 action 0xe frozen
Oct 17 01:01:33 Angband kernel: ata2.00: irq_stat 0x00400000, PHY RDY changed
Oct 17 01:01:33 Angband kernel: ata2: SError: { Persist PHYRdyChg }
Oct 17 01:01:33 Angband kernel: ata2.00: failed command: READ DMA EXT
Oct 17 01:01:33 Angband kernel: ata2.00: cmd 25/00:78:cf:a4:1b/00:01:0b:00:00/e0 tag 0 dma 192512 in
Oct 17 01:01:33 Angband kernel:          res 50/00:00:ce:a4:1b/00:00:0b:00:00/e0 Emask 0x10 (ATA bus error)
Oct 17 01:01:33 Angband kernel: ata2.00: status: { DRDY }
Oct 17 01:01:33 Angband kernel: ata2: hard resetting link

 

Does this sound like a loose/bad cable or PSU?

Try s new SATA cable.