OpenSolaris GRUB> boot failure HELP

Hi,

i am running an old Opensolaris 5.11 snv_111b on an x86 server. After almost 4 years of successful service, last night out of the blue started to refuse all connections to it's services, ssh, http,etc. The only visible solution at that time was a restart. But now instead of booting the machine stops at GRUB> prompt. Findroot returns zfs_read error : 15 File not found. Grub is 0.97 and i'm sure i did not perform any updates over night. Can i recover from this? the machine is pretty important still and i need at least eiter to be able to boot it again or recover the data there.
No hardware issues so far because i transferred the disks in an attempt to see if it is an HW error to a different identical machine and the symptom persists.
Any clues about the issue? How can i fix this?

regards,

Since there are few updates that are prone to modify the bootloader, rule out disk problems first. You may be having a crisis and need to backup immediately.

Managed to boot an opensolaris Live CD. Dmesg shows a failure on one of the drives.

The problem is rpool import shows the pool being online with a single drive but whenever i try to force the import using zpool -f rpool i receive the message that the pool cannot be imported because one of the devices is missing. i am a little confused. how come the pool can be online and not degraded or such