In my domain, I have two DCs running MS Server 2003. One of them also has the role of the DHCP server. For some reason, few users are unable to connect to this DC from time to time. After a few days (3-14 days), they are able to connect to it. Right now, my laptop is one of the ones that cannot connect to it. I can ping and connect to other computers and servers, except this DC. This has been going on for several months. Any thoughts would be greatly appreciated.
Are you getting any specific error messages? Is the issue happening at log in?
If you log in as a non domain user on the computer, can you ping the DC using it's domain name
In my limited experience, problems connecting to the DC has usually been an issue with DNS. If you can ping the server by it's IP but not its domain name, try removing all DNS servers from the client's interface accept one of your DCs and see if that helps.
Execute DCDIAG and NETDIAG. Examine the log to find any errors. That would be a good start. Do you have WINS on your network?