I've never heard of "Wireless isolation", and I've seen my share of router settings. First thing on the agenda when you want to do network things is to either get a non-retarded router, or preferably a wireless access point. Which most people SHOULD get. Not a full blown router. If you have not done that, you should go through the admin console on the device to check for odd settings. Oh, there's so many bad routers out there with strange settings.
When it comes to buffering, it might just be that your computer is not that fast. The server probably do on the fly conversion of the video, and that is quite demanding. Try to set the conversion settings to a lower quality, and see if that makes any difference.