I was wondering if anyone else has run into this bug ? If your copy of ME3 locks up you entire Xbox every time you load up the game when signed in, but it loads fine without a GT or another GT, then locks up your Xbox as soon as you try and sign in your GT that you've been playing with. Congratulations you also have the ME3 curse, and are completely unable to play it until Bioware have figured out what the problem is and patched it.
There is a thread on the Bioware forums where they have acknowledged the bug and said they are looking into it, though its mostly 20 odd pages of excessively indignant and impatient people whinging.
Bloody typical though that it happens to me less than 24 hours after saying to a friend that i would be surprised if Bioware had managed to leave a game breaking bug in the final build. *sigh*
I really should've known better.