Roaming Profile problem

I work on a domain with roaming profiles, and this is my
problem.

On many of my new XP machines, if I go to start, all
programs, it does not display a programs menu. if in XP
menu, nothing happens, if in 'windows classic', it
displays '(Empty).

There are definitely programs in the start menu, programs
folders in documents and settings.

I'm not sure whether it is the profiles that cause the
problem, I have a suspicion it could be something to do
with my domain also running 2000, and NT machines, and
when people have logged onto a 2000 or NT machine, then
an XP machine, it corrupts the roaming profile AND the
machines default profile.

If anyone can assist me I would be eternally grateful!

thanks

ste.