I've been struggling with the same box for a week now. At first I thought I had success...
After six years of faultless running, Drive 1 died. Of course, these are all IDE drives, and they are scarcer than hen's teeth in the styx in Panama... So I put an Ultra IDE to SATA adapter in, and the first time I powered it up (Buffalo first, SATA external enclosure and its supply), Drive 1 showed as disconnected. Power down. Power up the external SATA first, 10 seconds, then the Buffalo, and all is well. The Web interface let me Configure Drive 1 (which it saw correctly as a Seagate 500GB, compared to the 3 WDs that were in there too). It reinitialized the RAID5 array, and for about 12 hours, all was happy.
Powered down, went to sleep.
Next day, powered up the SATA, 10 seconds, powered up the Buffalo, and after about a minute of Christmas tree including the Drive 1 Red flashing and Diag Red flashing lites, it went in to power off. This repeated itself several times.
Finally, unplugged the IDE to SATA interface card from the Terastation motherboard, rebooted, and I'm running my 3 drive non-raid-protected storage. It's been running fine that way (well, walking sort of okay?) since...
Any insight or advice, other than... spend some more money??
BTW, it's running Firmware version 1.12... perhaps upgrading it to the current 2.03 from 2007?
One more question: with the box ripped open, where is the serial console that I can tap in to and let me watch what's going on directly? Any ideas? I don't really want to hack open that UPS connector -- just yet...