Slow shutdown/restart on all computers

Within days of upgrading my domain to Win2K last March I noticed that all Win2K servers, desktop and laptop computers were taking longer to shut down or reboot. They would get to the blue screen and sit there for 60 seconds, sometimes even longer, before finally giving up and shutting down. Sometimes I get an Event ID 1000 “DETAIL – Access is denied. Build number ((2195))” but I have no roaming policies in the entire company. Just in case, I made a domain policy to change the unload roaming profile retry count from the default of 60 down to 5, but that did not change the slow restart and shutdown times. I have watched new computers with normal shutdown times go immediately slow as soon as I join them to my domain.