9.3. Identifying and Resolving Logon Issues
Users must be able to log on to a domain to access domain resources. Thus, if they cannot log on, it quickly becomes a critical issue for the user. You'll need to be able to identify and resolve the problem as quickly as possible.
Many of the items just require looking at the symptoms. That may seem obvious, but for some end users an error message just indicates that things aren't working, even if a message clearly says the password has expired and needs to be changed. If it's the first time the user has seen the message, it's translated simply as "it's broken."
Here are some of the items to consider when troubleshooting logon issues:
Hardware versus network problems
Using cached credentials