Can't modify partitions

[James Taylor]

I have a disk /dev/da0 currently partitioned as one 36
gig partition, with no point point specified.  I'm not
sure how the mount point got through like that, but it
seems that because of it I'm unable to make any
changes to the disk.  I go into sysinstall(can't run
disklabel - it's a sparc64 machine)->Custom->Label and
delete the partition (/dev/da0d).  I then go to write
the information and come up with "ERROR: Unable to
write data to disk da0!".  No matter what I do I keep
getting this error when trying to make any change to
the disk.  

I've tried doing something like "dd if=/dev/zero
of=/dev/da0d count=1000000" trying to just wipe out
the MBR and maybe get a little bit more for good
measure, but that didn't seem to work.  Doing any dd
operations on just /dev/da0 come back with Operation
not permitted (I'm assuming this is intended
behaviour?)

How do I clear the partition information on this
drive? It's been driving me nuts for the past week or
so.

Thanks

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