Avoid setting page as parent id, which has current page as parent.

app/helpers/pages_helper.rb

@@ -50,6 +50,10 @@ module PagesHelper
   end
 
   def parent_pages_to_select(current_page)
-    Page.non_redirected.reject { |p| p == current_page }
+    unless current_page.homepage? # Homepage is the page trees root!
+      Page.non_redirected.reject { |p| p == current_page or p.ancestors.include?(current_page) }
+    else
+      Array.new
+    end
   end
 end

app/models/page.rb

@@ -32,11 +32,15 @@ class Page < ActiveRecord::Base
 
   named_scope :non_redirected, :conditions => {:redirect => nil}
   named_scope :no_parent, :conditions => {:parent_id => nil}
-  
+
   def self.permalink(title)
     title.gsub(/[\/\.,;@\s]/, "_").gsub(/[\"\']/, "")
   end
 
+  def homepage?
+    permalink == "Home"
+  end
+
   def set_permalink
     unless title.blank?
       self.permalink = Page.count == 0 ? "Home" : Page.permalink(title)