There is a contact form linked to from the GameSpot Help Center, which can be used for cases such as this. It does not require a login, so you can just fill in your new/current e-mail address. I would provide a summary of what has happened, including your username and old e-mail address. However, I would not include your credit card number or other sensitive information as the form and e-mail is not secure. Instead I would request that they provide you with a phone number that you can call, through which you may provide proof of your identity.

Good luck.
John


P.S. It might be a good idea to keep a list of people and services you give your e-mail address(es) to, making it easier to send out notifications and update account information and thereby reducing the chances of ending up in this situation again.