Had the same problems for ages, but just got through to online support, and basically they said to unlink your account, then sign up for a new account and link your console to that. Just did it and it all works fine now.

On the other point, if you still want to leave your clan, or anyone else wants to leave theirs/join a clan, The mentalists are looking for new members. We are only 12 at the moment, so don't get far in the clan ops, but most of the daily clan challenges we gold or silver, so if you're interested, apply online or send me a message and i'll send you an invite. Don't care about any of your stats, so long as you are prepared to play ...