I'm blaming the CD-R media - Verbatim AZO printable, re-order code #43309 - which I picked because the Internets claimed that it's good quality (bad Internets. No cookie for you). I don't know whether it's a bad batch or just dodgy in general, but nothing I've got quite agrees with it. The laptop's Hitachi-LG DVD±RW drive will happily write to blank ones, but then can't read them once written to. The Plextor PX-755A DVD±RW tries very hard, but ultimately fails to detect the media. Even an ancient Plextor 48/24/48A CD±RW drive (kept precisely because it can read anything) has to think about things for a bit before finally managing to read/write the discs.
Sigh. Anyone know which CD-R brands are worth getting these days?
As to why I'm still occasionally using CD-Rs in this day and age? Well, it's rather hard to burn an audio DVD... (that, and they're also handy to send someone a set of photos as a present, and a DVD-R seems like overkill for a mere 100MB).