That happened to me too until I figured it out. nah man after you downlaod that thing from the market place dont launch it.
Go to MY GAMES and then find XNA games in the top nav that goes left to right…. from that menu you can download the games. After you download the games you can play them in the same list as all your other XBL games.
IF you try to launch the XNA apps you download you will keep getting that membership error so dont do it that way. Downloading the xna apps you have gives you the extra menu at the top of your games list to get to the individual xna game downloads. I hope that makes sense. it took me a minute to figure it out. Get that samurai game though shits tight.
