vista beta 2 fails configure extender xbox360 error71

I have tried repeatedly without success to setup my Xbox360 with Vista Beta2. I get past the enter verification code to the configure settings step for the PC and the extender and it either locks up or eventually (after 10 minutes or so) states the configuration has failed. Message on screen says it should take 5-30 seconds. I also get a black screen of death on the Xbox360 stating error 71 (E71). Powering the Xbox off and back on resolves error, back to the dashboard just fine. I had my Xbox360 previously connected to an XP Pro box with Media Connect and a MCE2005 rollup2 box without any problems. I am using a wired ethernet network through a Belkin router. No third party virus or firewall. No other apps running during this process. Help please! Thanks.