If there's a "!" sign next to "Accounts", that means that there's a problem with your account. It could be possible that your profile is corrupted, so you should delete it of your HDD and then recover it back (You need to e-mail and password). Your profile could also be glitched in the system. That doesn't mean you're banned, but there's a small error in Xbox's servers. I suggest trying to recover your account first, and if that doesn't work, contact Xbox LIVE Costumer Support.