Share access slow after upgrade to 2003

We upgraded our File Server Domain Controller from Windows 2000 Server to Server 2003.
Share access used to be really quick.
Now there are a couple of seconds between access to shares.
If you are moving a few levels throughout shares, this becomes problematic.
Does anyone know of any documents that explain the exact process the OS goes through to access a share?
Could it be the new security settings that Windows 2003 employs add a few seconds of overhead to accessing that share?