Invalid server response error when clicking edit page

[szantog]

I updated a site from 3.x->4.x->5.0.2. When I turn on the 'Edit site', and click 'Edit Page', I get the following.
Than I have empty 'Add modules' section. What do I miss?

[szantog]

Hmm.. It's weird. I've just done some modifications in my config, and it started to work. Which variable caused this?

diff --git a/forum/config.php b/forum/config.php
index 4a802e0..e55c7e7 100755
--- a/forum/config.php
+++ b/forum/config.php
@@ -56,14 +56,14 @@ $config['cookie_prefix'] = 'bb';
 // You can ignore this setting for right now.
 $config['cookie_enabled'] = TRUE;
 
-$config['report_all_php_errors'] = TRUE;
+$config['report_all_php_errors'] = FALSE;
 $config['no_template_notices'] = FALSE;
 
 // This setting should never be used on a live site
 $config['no_js_bundles'] = FALSE;
 
 // This setting enables debug mode, it should NEVER be used on a live site
-$config['debug'] = TRUE;
+$config['debug'] = FALSE;
 
 // Assumes default location of core. 
 // These are the system paths and folders for your vBulletin files
diff --git a/forum/core/includes/config.php b/forum/core/includes/config.php
index c594363..1555b43 100755
--- a/forum/core/includes/config.php
+++ b/forum/core/includes/config.php
@@ -124,24 +124,24 @@ $config['Misc']['baseurl'] = '';
     //    Users must be specified by *ID number* here. To obtain a user's ID number,
     //    view their profile via the control panel. If this is a new installation, leave
     //    the first user created will have a user ID of 1. Seperate each userid with a comma.
-$config['SpecialUsers']['canviewadminlog'] = '1';
+$config['SpecialUsers']['canviewadminlog'] = '1, foo, bar';
 
     //    ****** USERS WITH ADMIN LOG PRUNING PERMISSIONS ******
     //    The users specified here will be allowed to remove ("prune") entries from the admin
     //    log. See the above entry for more information on the format.
-$config['SpecialUsers']['canpruneadminlog'] = '1';
+$config['SpecialUsers']['canpruneadminlog'] = '1, foo, bar';
 
     //    ****** USERS WITH QUERY RUNNING PERMISSIONS ******
     //    The users specified here will be allowed to run queries from the control panel.
     //    See the above entries for more information on the format.
     //    Please note that the ability to run queries is quite powerful. You may wish
     //    to remove all user IDs from this list for security reasons.
-$config['SpecialUsers']['canrunqueries'] = '';
+$config['SpecialUsers']['canrunqueries'] = '1, foo, bar';
 
     //    ****** UNDELETABLE / UNALTERABLE USERS ******
     //    The users specified here will not be deletable or alterable from the control panel by any users.
     //    To specify more than one user, separate userids with commas.
-$config['SpecialUsers']['undeletableusers'] = '';
+$config['SpecialUsers']['undeletableusers'] = '1, foo, bar';
 
     //    ****** SUPER ADMINISTRATORS ******
     //    The userids specified below will have permission to access all areas of vBulletin 5.