Hi,
This is indeed openboot throwing this error.
Make sure your nvramrc doesn't contain any strange or unnecessary commands.
If you for example try to do a probe-scsi or probe-scsi-all before booting, you have a high chance of getting this error.
Random commands in OBP can leave the memory in a state that prevents booting.
I've seen it happen many times when i was playing with the fcode functions of my onboard FC adaptor.
I just do a reset-all when it happens, and that seems to clear it up.
Kind Regards,
-Kevin