Back in January there was talk of the ZiO SmartMedia card readers not working with OS X 10.1.3 (see this hint and follow ups).
Last night I upgraded X to 10.1.5, downloaded the latest drivers from ZiO, and it all worked tickety-boo! I don't know which of these actually fixed the problem, but do I care?
Mac OS X Hints
http://hints.macworld.com/article.php?story=20020629113904986