DC failure after Remote Access role

We added the role of Remote Access/VPN Server and
Terminal Server to a primary Windows 2003 server that is
an existing domain controller, DNS server and DHCP
server. For some reason that process corrupted some files
for an accounting package on a shared network drive, so
we removed those roles. After removing and restarting the
server, login rights were increasingly reduced until the
domain is no longer available on the LAN. When first we
logged in after removing the roles, the workstations were
blocked from mapped drives, with an error message stating
that there had been an attempt to compromise security. We
looked at rights and shares on the server and looked for
an event log that might explain why the server was
locking out users (no event log seemed to address a
security alert or a login failure). We created a new user
and were able to login on a machine that had not yet
joined the domain. But as we went around the network, the
availability of services from the server seemed to reduce
step-by-step. For example, some workstations would login,
but no access to shares, then the same workstation would
no longer authenticate, then it would authenticate, but
not see the server listed as a machine in the domain,
then the error of domain not available would be as far as
we could get. We can ping the server, but we can't see it
in the network places. The DHCP seems to be working for
workstations. But no domain is available any more. Please
inform us if there is a security override of some sort
that we can apply to restore the role of domain server.
We made a full backup before attempting the new roles
that caused the problem, and we still have full
administrative access to the server itself. Many thanks.