No, but I'm guessing that M$ have deliberately changed something to screw the samba team.

The only difference between 2000 and XP that I know of that affected Samba is the certificate authentication policy with domain controllers. Under 2000 it was optional by defauly, XP had it set to mandatory. Beyond that, the typical clear text password authentication issue that older Samba servers required changed is still there. Nothing as far as I can tell about offline dealings with domains.