on the machines that are failing, check the service status in the services
tool -If needs be, stop the service and then restart it and see if that
helps

Martin Spencer-Ford
(TpwUK)

Check that the remote registry service and server service are started on
those problem computers and look in Local Security Policy to see what
registry paths are allowed access remotely and compare to a computer that
does not have the problem. Leave the firewall disabled [assuming that does
not make the computer vulnerable] until the problem is found. Also look in
the security logs on the problem computers to see if any logon failures are
recorded. Local Security Policy would need to show that auditing of logon
events was enabled.  The administrator should be able to access and
administrative share on the problem computer such as C$ which would be a
good test to try also to check for basic file and print sharing access to
the problem computer.   --- Steve