I ran into this problem today.
The solution for me was to connect the system’s hard drive to a standard PC, boot up with knoppix, and then use dd to zero out the beginning of the drive:
dd if=/dev/zero of=/dev/hda
This system had been set up with Solaris 10 prior to this. I don’t know why the kernel throws a fit when it finds a sun disklabel, but that is what appears to be the trouble.
Lee