samba - Aug 2005 - What's this error?

Hello all.

Logwatch reports this:

 **Unmatched Entries**
 rpc_client/cli_netlogon.c:cli_nt_setup_creds(256)  cli_nt_setup_creds: 
request
challenge failed : 288 Time(s)

And syslog this:

Aug  3 04:09:48 hanover winbindd[1746]: [2005/08/03 04:09:48, 0]
rpc_client/cli_netlogon.c:cli_nt_setup_creds(256)
Aug  3 04:09:48 hanover winbindd[1746]:   cli_nt_setup_creds: request
challenge failed

What does it mean, and what's the fix?

Many thanks.

Dimitri