What exactly is the client doing when you try to restart it? Is it just not responding at all, or is it giving you an error message?
Can the client computer actually still see the server running SetiQ in Windows Explorer? If so, make sure that you can ping the server's IP address. If you can ping the server, then make sure that the Registry entry to start SETI still has the correct IP address and is still pointing to the right path for the client.