Sergey,
I've seen 'client not allowed access' errors when there are network issues.
Can you connect toe the clients from your master server's Admin Console and retrieve their Host Properties? Do you get the same error?
If yes, are your clients and master in different domains? You can try adding the master's domain to the 'DNS Name Resolution List' in the network properties of the clients. That is what usually fixes my (46)'s.
Another thing to try: adding HOSTS file entries on the master AND clients. Add entries for all the clients onto the master, and add an entry for the master on all the clients.
$0.02