win2k sever upgrade/logins

WORKSTATIONS-WIN2K/SP2
SERVER-WIN2K SERVER/SP2

AFTER UPGRADING NT4 SERVER TO WIN2K, LOG-INS ARE NOW TAKING FOREVER?? WHY MIGHT THIS BE??
IF I DISCONNECT THE NETWORK CONNECTION,PRIOR TO BOOTING THE MACHINE, LOGIN IS AS QUICK AS IT ALWAYS WAS, AND I CAN THEN RE-ESTABLISH CONNECTIVITY ONCE I AM UP.