user account domain profile not loaded!

Hi y'all,
I run a Win SBS 2003 R2 for our server OS, we've been using WinXP Pro for
our computers OS; but there is a new computer came with Vista Business
edition OS lately.
The employee who already has his user account domain can't login properly
into that Vista computer, it keep saying that the profile can't be loaded
properly thus it will keep using temporary profile instead; so the user can't
save any changes he make in that Vista computer.
But there has been no complain or problem if the user access the WinXP Pro
computer, everything is going fine. So far the user will have to keep using
the old computer, although we're planning to replace every computer's OS with
Vista Business nowadays...
Anyone know what happen there and how to fix it?
Thank you!