Save the query into a var and echo the var to see how it looks. From what you've presented, all seems ok, except maybe DESC is parsed as modifier, and not as field name? Try to enclose field names into single quotes:
INSERT INTO 'specials' ('product', 'desc', 'offer' ...
BTW, never put string $_POST vars directly into query, pass them through mysql_real_escape_string(), and if it contains strings that will be presented back to the user, clean it of HTML tags.