Hi all, I am looking after a 10.5.1 Mac OS X Server at my office. It originally had Tiger Server installed and all was running smoothly as far as I was aware. I upgraded it to Leopard a couple of weeks ago for the new features. I did a clean Erase and Install rather than an upgrade after having problems with vanilla Leopard in the past. Something has happened over the past couple of weeks that is causing the server to deny users access. Clients can't login, and shares aren't available to non-managed machines. I can't even use Server Admin remotely to check the server status. Now here's the really weird thing... If I go to the server and try to login using the System Administrator's account the login panel wobbles, even the root user's account won't work. The only thing I can do is a restart. In Workgroup Manager I set a profile to disable Restart and Shutdown from the server's login panel and as you can imagine I couldn't log in to restart the machine so I had to do a hard restart! (eek). After a reboot everything is fine for a couple of days then it happens again, a denial of access. On the managed client machines I get a green 'Network Accounts Available' notice so why can't anyone login? I have tried to check the logs but can't find anything that seems to be pointing towards the problem. The server is running, DHCP, DNS, NAT, VPN, Firewall, OD, SMB. Settings up DNS and DHCP was a real pain but I thought I solved that after reading someone else's trouble with what the install wizard does/doesn't do properly. The server was set up using the Advanced configuration. I can ping the server and other non-managed clients continue to get Internet access so I can assume that the NAT and Firewall services are still running. Has anyone come across this or point me in the right direction to start investigating. Thanks for any advice.