Duel Booting XP & Vista Business

Hi,
My duel boot computer with vista business/xp connecting to the office domain
(small business 2000) works fine until you reboot and connect to the other
OS and you can not log in as you get this error: windows cannot connect to
the domain because the domain controller is down etc.
you have to log in as a local user then reconnect the the domain then reboot
then it will work? but you then get a similar problem with the other OS? its
a pain the keep reconnecting to the domain all the time.
Can anyone help please!

Regards
Michael