John,
Have you considered the possibility that the packages are corrupt due to
truncation which may have happened because you (or your mirror) ran out
of space at some point in the past while downloading these packages?
The package names are late in the alphabet, which might account for why
only these few packages are affected. Also, the corruption need not
have been recent. My xpilot package has not changed in a very long
time, which might account for the persistence of a very old one-time
corruption event.
Ben