Sign on at http://billing.microsoft.com with your subscription LiveID. You will see the last 4 digits of your credit card listed under the OneCare subscription.
It seems like Firefox and Safari are blocking the redirects that happen when you try to launch a URL from within OneCare, which is where the "g" comes into play in the URL.
Note that OneCare will not be free, but a replacement product will be offered that only includes the virus and spyware protection. The full OneCare product will be available through June of 2009 and supported through 2010.
Yes, many subscription type services will be allowed to be charged when you have a card stolen and a new one issued. You'd need to contact the issuing bank to dispute the charges and discuss options.
-steve