Moved the site to a new server, but there are problems

Once I moved all the files and connected the database, the site worked fine, but the www. did not. I redirected the www. through cpanel redirect and root redirects beautifully, but the rest of the site other then root does not. It is not a problem, of course, if I get some one new to browse, but what if some of the pages got catalogued by someone and linked through the www. protocol?
Anyway, here is the message I get: Warning: Cannot modify header information – headers already sent by (output started at /home/victoria/public_html/wingedtreasures.com/wp-content/plugins/favorites-posts/favposts.php:12) in /home/victoria/public_html/wingedtreasures.com/wp-includes/pluggable.php on line 890

I am new to WordPress and a little fuzzy on php as well.