Event 4625, Microsoft Windows Security Auditing

I have a Windows Server 2008 R2 set up as a Hyper-V server. The server is a member of the domain running on the hosted virtual servers, but does only use local administrator to log on.

After changing the password on the local administrator account it has started generating about 10.000 audit failure events 4625 every day.

No servers or Workstations are using any resoures on this host server. There are no local services that uses the local administrator to logon.

The Network information in the error message is blank, so I am not able to figure out where it is comming from. Network logon type (3), but no source name or address.

Any suggestions as to what can be the cause of all these error Messages?


Thanks

______________________
The error message is:
An account failed to log on

Subject:
-Security ID: NULL SID
-Account name:
-Account Domain:
-Logon ID: 0x0

Logon Type: 3

Account for which Logon Failed:
-Security ID: NULL SID
-Account Name: * local administrator*
-Account Domain: *local host name*

Failure Information:
-Failure Reason: Unknown user name or bad password
-Status: 0xc000006d
-Sub Status: 0xc000006a

Process Information:
-Caller Process ID: 0x0
-Caller Process Name:

Network Information:
-Workstation name:
-Source Network Address:
-Source Port:

Detailed Authentication Information:
-Logon Process: NtLmSsp
-Authentication Package: NTML
-Transited Services:
-Package name (NTML only):
Key Lenght: 0