I think the reason for this is that when you burn at a higher speed, the "on/off" transitions take up more linear space on the disc.
Ideally, on a glass-mastered CD-ROM, the transitions are hard, something like this:
But when you're writing to a spinning disc with a laser, things aren't that perfect. It takes time for the transition to happen, and the disc surface is moving past the laser, so instead of a nice hard edge, you get sort of a "ramp". This isn't so bad as long as the ramp is short enough, which is generally the case. The problem comes when you're writing at something like 48x and then reading the disc in a 1x drive, that ramp will pass by the laser much slower and will "look" 48 times longer than when it was written. This probably pushes things to the point where the mechanism gets confused about whether it's actually seeing a transition or not.
Modern drives are made with CD-R's in mind, so they probably have a lot more tolerance for "slow" transitions than older CD-ROM's that were only ever expected to read glass-mastered discs.
--Zero