I had a very odd problem today at work.
An employee couldn't connect to the file server (which is also the DC,DNS,etc). It's our main/only server(other than a print server). anyways, he was receiving a valid NIC/dns/gateway ip and could ping the server fine. Though when I tried to connect via \\server1 it timed out. I tried connecting via \\192.168.0.1 and the same thing happened.
I looked at our DNS service on the server and noticed there wasn't a (A) Host record in the FLZ for his login. I added it and after about 5 minutes he could connect fine.
I'm not convinced this was the problem though. If it was a DNS error, shouldn't I have been able to connect via \\192.168.0.1 ??