So as it turns out, the external enclosure in which I had my 500GB drive, is flaky.<br><br>I put the new 1TB drive in this enclosure to use as a backup drive. I put the old 500GB drive (that was giving me "can't read sector" I/O errors) on a small SATA-USB adapter I had. When I started copying from the old to the new, the new 1TB drive was giving all kinds of I/O errors.<br>
<br>I hung the 500GB drive off of an internal SATA interface of my PC, and I connected the 1TB drive to the SATA-USB adapter. Now, I am copying things over with no I/O errors.<br><br>What's interesting is, for the past 18 months or so I've kept this enclosure in a cool, dark closet... and I've only moved it once every 1-2 weeks to do backups. And I only plug it into a UPS-protected outlet.<br>
<br>So I wonder what, barring an external physical event, causes a transistor or two to work one day, and then the next, say, "you know what? I've had enough on/off cycles in my lifetime, I quit!"<br><br>Cheers,<br>
-JK<br>