I am managing an Xserve running Mac OS X 10.5 server. Recently, the login window has stopped working correctly. As shown in the attachment, the "login box" fails to appear. Rebooting the server fixes this temporarily (so far) but after a while the login box disappears again. I am unable to reboot the server frequently as it is hosting live applications (all of which continue to run normally during this error). Also I'm concerned that eventually a reboot will not fix the problem. I am able to login via SSH with an administrator account and have tried deleting com.apple.windowserver.plist from /Library/Preferences and killing/restarting just the loginwindow and windowserver processes. I'm at a loss - any suggestions?