If you go to sign in on a computer on a domain and it is taking longer than usual or anything more than a minute, try these steps.
You want to look for network slowness first, many times this is a failing switch or break in communication between the workstation and the Domain Controller.
Go ahead and login. Once in, Run =>
Create a DWORD and name it
verbosestatuswith a Data Value =
regeditand logoff the account. Now sign back in, I have seen this work multiple times.