Windows Server 2003 Autoenrollment

I have a Windows 2003 Server with a mixture of Windows 98 and Windows XP Pro clients. The 98 machines run fine, log on to the domain etc, but evry time I log on from one of the XP machines, I get an Autoenrollment error, I also get the same error every 8 hours thereafter. According to Microsoft, this is caused by incorrect DNS settings. I have checked the DNS settings in all of the XP machines, and as far as I can see they are fine. I have also checked that the DNS server is running on the 2003 server and that lookes fine too. Any ideas what else could cause this?