Which x86 platform is this?
Some x86 platforms seem to have trouble with setting the active boot partition.
If you can boot this system from media and set the active partition through the format-->fdisk utility,
that might help.
This is a desktop PC. We run about 900 Sun / Oracle servers in our shop - all in production.
Feedback on the solution:
The system was rebooted with the live CD.
gparted showed the HDD as /dev/dsk/c7t0d0p2
Partition Filesystem Size Used Unused Flags
/dev/dsk/c7t0d0p1 unknown 255.88MiB --- --- bios_grub
/dev/dsk/c7t0d0p2 unknown 465.50GiB --- --- ---
/dev/dsk/c7t0d0p9 unknown 8.00MiB --- --- ---
p1 needed to be made active.
Root access was obtained (jack@solaris) password solaris.
# format > fdisk > 2. Specify the active partition > type "1"
A reboot took the machine straight to GRUB - thank you.