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

Gemfile.lock

@@ -14,10 +14,10 @@ GEM
     haml (3.0.25)
     mysql (2.8.1)
     prawn (0.6.3)
-      prawn-core (>= 0.6.3, < 0.7)
+      prawn-core (< 0.7, >= 0.6.3)
-      prawn-format (>= 0.2.3, < 0.3)
+      prawn-format (< 0.3, >= 0.2.3)
-      prawn-layout (>= 0.3.2, < 0.4)
+      prawn-layout (< 0.4, >= 0.3.2)
-      prawn-security (>= 0.1.1, < 0.2)
+      prawn-security (< 0.2, >= 0.1.1)
     prawn-core (0.6.3)
     prawn-format (0.2.3)
       prawn-core

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)