Windows 2003 server netlogon error

Hi,

I have an XP pro client computer which is connected to a server 2003 domain. 50% of the time it is able to access files on the server normally. The rest of the time it can take several minutes to open a file and sometimes it will fail completely.

In the server 2003 log there is are several instances of a netlogon error which says that the server was unable to authenticate my computer.

I checked the list of client PCs on the server and this PC is not listed. However, the user is listed within users. Could this be the cause of the problem and should I add the computer to the list of clients?

Many thanks

Simon.