cannot find boot device and won't boot off cdrom

I'm running solaris 2.5.1. My main development server is DEAD, i can't even boot off the cdrom, it powers up, acts like it is starting the boot process but then says cannot find boot device. I've done the search here on this site and saw the other posts, but at the ok prompt it won't even let me boot off the cdrom. at OK i've tried boot -r , boot cdrom -s, boot cdrom, boot -a. It will not do anything with boot command. I've also tried the probe-scsi-all command it sometimes errors, sometimes shows my 4 scsi devices, but the Target 0 is blank or doesn't show up at all (i've tried probe-scsi-all 10+ times and get a different answer everytime). One of the boot messages I get at boot cdrom -s:

can't read disk label
can't read disk label package
cannot open /sbus@1f,0/SUNW,fas@e8800000/sd@6,0:f file and args: -s
panic - boot: could not mount filesystem

ANY IDEAS? i do have a spare system that I could open up and take out the main hard drive and swap. My data is safe, and I have backups, but getting the system running asap is a priority. it's our main development box for the programmers. any help much appreciated.

I've tried to boot off both the solaris disks, the solaris 2.5.1 and the solaris desktop disk. I've never seen anything where it wouldn't boot off the cdrom too, or the main hard drive.

wow, never saw this and not sure why it just happened, but the problem was end termination of the scsi chain. The last device had the wrong scsi id AND wasn't terminated. This has worked for over a year so not sure why it happened now, and not sure how those pins got changed, because when it was set up it was correct. but that was it completely. So hope this helps someone else.

how did you fixed it?