[Mediawiki-l] Header errors: I need help please.

[John W Foster]

I installede Treeview4.php in the directory indicated and edited the
LocalSetting.php to include the following:

###############################################################
##added by jwf 02/25/08 to install Treeiew4
include("$IP/extensions/Treeview4.php");
$wgTreeViewImages['plus']   = "Plus.gif";
$wgTreeViewImages['minus']  = "Minus.gif";
$wgTreeViewImages['opened'] = "Folder_opn_sml_yel.gif";
$wgTreeViewImages['closed'] = "Folder_sml_yel.gif";
$wgTreeViewImages['doc']    = "Doc-icon.gif";
$wgTreeViewImages['spacer'] = "Blank.gif";

Now I get this message:

Warning: Cannot modify header information - headers already sent by
(output started at /var/lib/mediawiki/extensions/Treeview4.php:246)
in /usr/share/mediawiki/includes/WebResponse.php on line 10


This seems to happen with a lot of extensions and only goes away when I
remove the extension. The install is to the letter what is supposed to
be done per the author.
Can anyone tell me what the problem is? 
Oh yeh: the extension does not work either.
Thanks!!\
frosty