I am unable to access shares using the NetBIOS name of a server following last weeks security hotfix application. Prior to the hotfix application the event logs were clean and share access was without issue.Problem context:Affected system - Windows Server 2003 x64 Enterprise Edition domain controllerThis system has a companion domain controller, also Window Server 2003 but 32-bit. It also has all hotfixes applied but does not exhibit the anomaly.All accesses described here are on a local subnet. No IP address changes have occurred. All systems are members of the same domain.Problem description:An attempt to access shares via Windows Explorer on the target server from multiple client systems return "\\computername is not accessible Logon failure: the target account name is incorrect".An attempt to "DIR \\computername\sharename" from a command shell returns "Cannot find path '\\computername\sharename' because it does not exist."These access failures are accompanied by Security Event Log records on the target server of Event ID 529 "Unknown user name of bad password". These are kerberos Logon Type 3 Failure Audit records.These errors occur when accessing administrative (C$) as well as non-administrative shares using the NetBIOS name by users with Domain Admin rights however SHARE ACCESS USING THE SERVER'S IP ADDRESS SUCCEED, both from Windows Explorer and the command shell.The problem behavior occurs from Vista clients as well as Windows 2000 Pro SP4 workstations.I have compared the SPN's defined on the target system to those on the 32-bit DC which does not exhibit this behavior and see no obvious discrepancies.Summary:A 64-bit domain controller received hotfixes and its shares are not inaccessible using its NetBIOS name in the path but is accessible using its IP address. Kerberos failure audit records are being logged in association with failed accesses.Please advise. Thank you

I know this is an old post but I'd thought I add my experience for those that may stumble on this. I was having the exact same symptoms as described, the NetBIOS name wouldn't work but the IP did. This occured after we decommissioned a server and upgraded to a new one. What had happened was the tech had named the new machine incorrectly. So the new machine had the same static IP but not the old NetBIOS name, however; the old NetBIOS name was still in AD. When trying to access the share it resulted in the issue described and led me down a rabbit hole. The NetBIOS name I was trying to access was still in AD and even pointing to the right IP but the real machine did not have the name anymore. I deleted the old AD object and renamed the machine to it's proper name to resolve the issue. Anyways so lesson learned. Check the name of the machine if you ever see this wierd error (as it's a very simple check).

@Nelis99 thanks, i checked the hosts file in c:\windows\system32\drivers\etc and sure enough found the problem you just described. Saved me from a system reinstall. Much appreciated.