I had some problems with "jquery-1.6.3.min.js" which has now resolved. While attempting to solve this I tried a suggestion I saw here in the forum to change the general options the address of the site and removed the "www." (http://www.site with) after that the site crashed. Only works if you use the address http://site.com.
It appears the error "Warning: Can not modify header information - headers already sent by" and already checked the question of the blanks before and after the php tags.
Since then I can not access wp-admin to reset this setting.
Does anyone have any suggestions that might help please?