We have 3 servers at 3 offices; all running AD and DNS member of the same domain. Everything has been running smoothly untill a couple of days ago. When users logged into the domain try to access resorces on the server using host names, they get the following error "Logon Failure; the target account name is incorrect". No error is logged on the server we try to access, but the following error is logged on the client computer "The kerberos client received a KRB_AP_ERR_MODIFIED error from the server host/can21lar.nlk. The target name used was cifs/CAN21LAR.NLK. This indicates that the password used to encrypt the kerberos service ticket is different than that on the target server. Commonly, this is due to identically named machine accounts in the target realm (NLK), and the client realm. Please contact your system administrator".

There are no identically named machine accounts.

We can access resources on the server using the IP address of the server.

If I run DNSManager on one of the other servers, it's the same; we cannot connect to the DNS server using Hostname (Access denied), but we can connect using the IP address.