Part of the PS CS3 installation includes "Bonjour" (C:\Program Files\Bonjour\mDNSResponder.exe). This is the problem and it can be disabled. It is located in services.exe but it is not written like this.
Look for "##Id_String2.6844F930_1628_4223_B5CC_5BB94B879762##" in the services and disable it. I did this before I reactivated PS and then activated PS with no problems. My network is normal and PS works too.
Hope this works for you as it did for me.
Dawn