Honestly, I didn't post a solution cuz I'm not sure it was anything I did. But, here goes:
On the fourth attempt, I deleted everything I could, then did a hard reset by holding the menu button down for 45 seconds (not the 15 as suggested in the manual). I left it connected, then ran a complete scan including connected drives (Results: 45 suspect items--unusually high). After that, it reformatted just fine and I was able to copy over everything I had on it before.
It was late, otherwise I woulda posted all that.
