Thank you guys for your reply. I have already used the "Contact Us" form. However, no response. Yes, I will try to register again. But I think it does not solve the problem. If I was banned prior to registration, it means that there is some black list. How do I remove my ip or other data which identified me as a spammer?
There is no automatic feature in vbulletin that bans people. Either you've been manually banned by an administrator, or else they have a modification installed that is banning you based on something. In either case there's nothing you can do except to try to contact them to find out why.