...and then I found this forum.
I was getting nothing but coasters. I thought I had tried everything: different media, different versions of Nero, different software, different speeds. I even (thought I had) made sure I had the latest firmware.
Then I noticed that people were discussing a newer firmware version than what I had. I flashed to 2.18 and now everything works! Thanks a lot for providing this service, moderators. I'll definitely be checking back in for updates.