Joined: Mar 2011
Posts: 63
I've had good luck with the following three options.
1) power cycle the Xbox. Don't just restart it, but actually hold the power button till it shuts off, wait a minute or 10 and start it back up.
2) Delete the user account from the Xbox. Once it's deleted, power cycle the unit. Once back on, add the account back on the Xbox.
3) last ditch effort, reset the xbox. I can't remember off the top of my head exactly how it's done, but it something like troubleshooting, repair or reset and you should be able to select to keep your user data.
Good luck