To change the hostname in Solaris 10 you need to edit 3 files and appply the new name.
/etc/hostname.*interface, e.g. hostname.bge0
/etc/inet/hosts this file is a hard link to /etc/inet/ipnodes. You will need to make /etc/inet/ipnodes writable before editing it. To enable write use the command chmod 744 /etc/inet/ipnodes.
Finally rename directory /var/crash, the system will automatically recreate this after rebooting.
# cd /var
# mv crash crash.old
Now reboot the server.