That happened to me as well, its a flooding security feature that is turned on by default. You hit the site to much, you gonna get banned. I used another PC with another IP addy (work/home), logged in as admin, went into the security options.
Made flooding inactive and then removed the ban on my primarily used IP addy.
Server specs (Server OS / Apache / MySQL / PHP / DragonflyCMS):
Joined: May 24, 2007
Location: Ft. Lauderdale