You may experience delays when logging into domains because of a Group Policy setting that controls how networking services are loaded during the boot up process. This speeds up the login process in a stand-alone workstation by allowing the user to log in with cached logon credentials before the network is fully ready, but can cause delays for a domain logon.
You can disable this through the Group Policy MMC snap-in. Under Computer Configuration-->Administrative Templates-->System-->Logon, change "Always wait for the network at computer startup and logon" to ENABLED.
This was first published in June 2004