Sounds like someone might have tried to gain access to your account.
As long as you can still access your account, and have complete control over it, I'd disregard it, but I do recommend changing your password.
If you don't have any access or control of your account, call Microsoft, or contact Xbox Support Via Twitter (not the forums, because I'll tell you to do the samr thing there

). They'll put you in touch with the PETs.