OS X Snow Leopard Server: trying to create a second virtual machine

I bumbled through the creation of a Snow Leopard Server VM as while back and it's working great.
When I tried to create a new, 'clean' second SL VM, the server setup process errored, saying that it could not find a keychain.
What I seem to have ended up with is a SL VM that I cannot log in to, as it won't accept the admin name and password.
I anyone has any helpful suggestions, or experience of Snow Leopard VMs, I'd appreciate advice.
Steve