Having just endured about 12 hours of pain due to this disklabel
VS msdos deal, let me suggest a workaround (for now, till this is
repaired).  The current logic in disklabel is:

  look at the bootblock, read a partition table if there is one,
  and latch onto the partition marked A5, or failing that, the first one.

  look at the disk label to be written.  If:
     there was a partition found above AND
       it has a nonzero size AND
          it's an A5 partition AND
              its offset is the same as the C partition of the
              label you are trying to write, then
       (write it at the beginning of said C partition)
    ELSE
       fuck you over big time (but tell you about it).

  Note that for the purpose of BOOTING, you look at the first number
  in the pfdisk printout, but for the purposes of matching up for disklabel,
  you use the second--one is the beginning head, sector, and cylinder, but
  the other is the sector offset from the beginning of the disk.  These
  numbers have to match perfectly or you are SOL.

DG