Changing your registered e-mail address has no effect on your Cnet username, which does not offer a 'change' option. If you created a new account you'll need to logout and then log into the new one, but if you just updated your e-mail address the only change should be that your e-mail goes to your new e-mail account instead of your old one.
John
I changed my email address in CNET after receiving too much spam. The domain name is the same, but I changed my name like Mike1 to Mike2. Yet, CNET web site refers to me as Mike1. My email address is Mike2.

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