SSIA. I believe it's because /bin/cat doesn't exist on the initrd (so the check of /proc/ide/blah/media doesn't work). But that's just a guess at this point. Seemed to start happening with the upgrade from kernel-2.6.9-1.649 to kernel-2.6.9-1.667, and from udev-039-6 to udev-039-8.FC3.
No, the missing 'cat' doesn't appear to be it.
Oddly... turning *on* logging in udev.conf fixes it.
seems like the /proc file does not exist, if udev is too fast...
fixed in udev-039-10.FC3.1