This was a new machine (although when I say new, we purchased it a little while ago).
Powered on, and the preinstalled Solaris just panics. Not necessarily a problem, as I reinstall anyway. But I have seen this a few times - the preinstalled system should at least boot.
So I boot using Solaris 10 10/08, and it dies on me:
Fast Data Access MMU Miss
What I has to do was install Solaris 10 5/08, update the system firmware, and then install the version of Solaris I wanted.
(Which explains why my other machines are fine - they were first installed a little while ago, so has S10 5/08 on them initially. But it looks as though updating to reasonably current firmware is a really good idea.)