Why does my Blackjack II go to "Forbidden 403" every other day when I try to access the web. Settings are OK.

AT&T says that all the settings are normal and no one can figure out why it refuses to return to ANY web site and gives me the "forbidden 403" message. When phone is re-booted (turned off then restarted) then it will access any page on the browser for a day or 2. My original Samsung Blackjack did not do this.