Hi Ahmed,
As fas as I understand, the current problem is that your master machine cannot connect to slave machines using the Network Suite features. Since it does not matter for TestComplete whether the remote machines are machines on your LAN or machines accessed via VPN, the problem should not be related to the way you connect to them (unless your VPN connection is broken). First of all, take a look at the following SQAforums thread, it contains a number of steps you should try too:
http://www.sqaforums.com/showflat.php?Cat=0&Number=610518&an=0&page=0&gonew=1#UNREAD
Also, I recommend that you see the "TestComplete Network Activities - Possible Issues With Antiviruses" help topic.