I got the LaCie Big Disk Extreme 500GB backup drive back today. LaCie is suggesting it was just a firmware issue, so they thoughtfully updated the drive, nuked the data that was on it, and returned it. Over a month after it died. Going a month without any kind of backups is a little scary. Here's hoping it was just a firmware issue - the drive checks out OK now, and already has over 100GB of backed up data on it (and growing - likely will be close to 200GB by the end of the day) - and that's only 2 servers backed up...
Update: A few hours of unattended backing up later, and I've already burned through 214.79GB of space on the drive - including a full Carbon Copy Cloner image of my laptop's drive, and all critical files from the two servers that I care about (and can still access). Whew!