Using a Mac Pro 2,1 fitted with 4 750GB drives in RAID 5 with the Apple RAID card. I noticed this computer was fitted with two extra eSATA ports using the two extra SATA ports in the motherboard. So I bought a 2TB Seagate and a 2 bay eSATA enclosure from OWC. Everything worked for a while but the drive started to dissappear once and a while which needed a reboot. But now the drive isn't recognized at startup. I can reformat it with Disk Utility, but if I try to do anything like transfering files it becomes intermittent, or Disk Utility cannot even verify or repair the disk. Then it looses the partition entirely. The disk shows in System Profiler, but sometimes after problems the System Profiler says there was a problem with the SATA bus (an error has occured). Firmware is CC32 which is old. I bought a new drive and the same problem occurs, this one has firmware CC35. I tried to switch cables and ports, same thing. I am a bit at a loss what to do.