server 2003 logon takes longer than NT 4

I am setting up our first MS Small Business Server 2003 server. Until now we only had a single nt 4 server. I am noticing that user logon from an xp pro client takes considerably longer with 2003 than it did with nt. Is this normal? Is it because of active directory or have I goofed up my new 2003 server somehow? I am using the same xp machine just joining the new domain. I expected the initial logon to take longer, but every logon takes over a minute longer than it did with the nt domain. I have tried switching back to the nt domain and it is still ok – only takes a few seconds to logon. But when I try again with the 2003 domain it takes over a minute. I have also tried other client pcs with the same result.