Im trying to play my pc media via xbox 360. So when i start up wmc i go to tasks -> add extender. I punch in the 8 digit code it wants from the 360 and when i click next it says an error has occured wmc will restarts itselfYou can communicate with the xBox normally on the network? And it does show up in the Media Stream settings in the Advanced Sharing settings and you do have media streaming enabled?
What exactly are you trying to do with the xBox, and how? Are you trying to stream music or video to a TV? Are you starting the streaming from the xBox?
Since I don't have one, it is hard for me to see what might be wrong, but maybe someone else will.