I was using Server Assistant to do a remote setup of Mac OS X Server, and for some reason Server Assistant hung. When I relaunched it, the target server would not allow me to start over or continue the remote setup, claiming that it was already being remotely configured (clearly it didn’t notice that Server Assistant barfed).
I SSH’d to the server as root / [first 8 chars of serial number] and begun to poke around. Typically, OS X leaves little breadcrumbs in certain areas of the filesystem as state indicators, such as /var/db/.AppleSetupDone which is created after you go finish the setup assistant. However, this file was not there on my target server (and it shouldn’t have been, since I never did actually finish the setup). There was also no ‘setup in progress’ file in /var/db. After running fs_usage -w for a brief minute, I found what I was looking for: /System/Library/ServerSetup/.RemoteSetupInProcess. After nuking this, I was able to start again with the remote setup, and all is well.