Windows Login Issue with SQL 2000 and Windows 2003

Here is the situation. I have 2 servers running the SQL version of Navision Attain 3.6 on SQL Server 2000. The first server is our current live server which is running windows 2000. We are replacing it with a server with beefed up hardware running on windows 2003 server. Server 1 = Windows 2000 Server 2 = Windows 2003 Server 1 is running windows login now and works perfectly. Server 2 has the extended stored procedure setup just like Server 1. However Server 2 when logging in tells me the “The combination of user ID and password entered is invalid. Try again”. I can change the server name to point back to Server 1 and it logs in fine. I have sync’d the database users from the Tools->Security menu. I have even tried deleting and recreating a user in SQL 2000 to see if that fixes it. I have removed the extended stored procedure and recreated it (xp_ndo_enumuserids). I verified the xp_ndo.dll was in the SQL Server Binn folder. I am out of ideas and begining to think it has something to do with Windows 2003 since that seems to be the only difference between server setups. Any ideas?

On the bad server can you do in Query Analyzer: exec xp_ndo_enumusersids What is the result? A thought in advance: If you are using NT Fibers on this server, it will prevent this proc from working. This can be disabled in Server properties from Enterprise Manager.

NT Fibers was the problem. I have removed that option from the SQL Server Setup and windows logins are functioning normal. I was giving NT Fibers a try to see if there was any speed boost when using it. Thanks for the help.