Jan 12 09:22:36 Edit1 com.apple.loginwindow: -xaDiskDisappeared: removing "_windowserver" with home "/var/empty" from DSLocal because disk disappeared.
‘xsDiskDisappeared’ is a function of external accounts in Leopard. External accounts are a new feature that you can use in managed environments. They allow you to let a home directory for a user be created on an external disk. Very handy, especially in (for instance) a school with a lab full of Macs. Let the students carry their home directory with them on a USB drive or an iPod.
What we have here, though, is a disk with Leopard installed is being treated as an ‘external accounts’ disk, and when it’s removed, the system is deleting the users. In this case all of the system users. If you disable external accounts on the Open Directory Master, this should stop happening.
On a related note, I tried to trick my trusty PowerBook G4 into letting me use External accounts without being bound to Open Directory. No dice. I did get a home directory on my iPod by adding a user using Workgroup Manager, and specifying my old iPod as the location for that user's home. Automatic creation of the home directory will fail, though, and the whole thing was just ugly.
On a related note, you can use Workgroup Manager to manage a whole range of interesting things on your Mac. But I'll get to that later.