So I've been having this problem for a couple days now. When on the dashboard I can sign into xbox live, view my friendlist, chat in party. What I cannot do is the following
1. See my achievements
2. See my own avatar (appears as the generic grey sillohette).
However, anytime I put a game in, I am IMMEDIATLY disconnected from xbox live, no warning message or anything, I am just disconnected. If I try to reconnect from in game it will tell me that it cannot connect to xbox live. If I go back to the dashboard I can sign in again but once I boot up a game I am immediatly disconnected again (regardless of game). I have tried clearing the cache which has had no affect neither has any reseting on the modem or router.