Try using (the dread) IE browser. If you can log in with IE but firefox still wont except your password. Then its likely a corrupted cookie.

in firefox. in the toolbar. Click tools >clear private data> check cookies
Be careful because this will erase all your cookies as well as anything else you leaved checked, like browsing history or downloads.

Clearing the cookie for this site should allow you to login, which will create a new cookie thats not corrupt. Then the site should work fine in both firefox and IE.

Also note at times we ban heavy spam emails, such as gmail. If registering you see account has been banned. Its probably because of spam and not related to you as a player here. While gmail is a very popular email for people. Its also heavy abused by spammers.