ZFS, chflags and installworld

Hi everybody,
I successfully moved everything to ZFS a few weeks ago. Everything  
seems to
work, except I can't run installworld. If I understand things  
correctly, ZFS
doesn't support chflags, but I'm guessing the flags stuck when I  
copied the
files from UFS (using tar)?
In any case, installworld gives me plenty of errors like "chflags:  
(filename):
Operation not supported", and the files remain unchanged.
kern.securelevel is -1 and has always been.
chflags -R noschg doesn't work (plenty of "Operation not supported"  
errors).

Any hints?

Thanks,
Thomas