At OK prompt boot cdrom -s, check /etc/vfstab for any problems or try to cd /var; ls -l /var, check if there is adm directory is there, if not Mkdir adm and cd adm.
pwd
/var/adm
ls -l
check out if you have these files
utmp, utmpx and so On. if do not have, such create them
touch utmpx
touch utmp
then, reboot the system
.
F. regal
good luck
"think twice and hit enter once"