Can’t log in or change password. Error -14120

My clients 10.4 Xserve "crashed" in some way yesterday, I'm not sure exactly what happened but someone decided to power the Xserve down and back on again. All was well after the reboot - for them but not for me. I cannot log in using either my admin account or as root which was enabled. If I log in using another users ID , I can see my account in WGM, but if I attempt to reset/change my password then I get the following "The password coulc not be set. An unexpected error of type -14120 occured All other settings were saved". Netinfo manager suggests that root is still enabled but again I'm unable to login as root. Intersetingly I can use my username and password to authenticate keychain access and other apps, but not log in. Anyone have any (hopefully not too tehnical ) suggestiond? TIA Huw