diff -bNaur redSVN1797/app/controllers/projects_controller.rb redmine/app/controllers/projects_controller.rb
--- redSVN1797/app/controllers/projects_controller.rb	2008-09-11 16:44:59.337389000 +0200
+++ redmine/app/controllers/projects_controller.rb	2008-09-11 08:57:41.546391600 +0200
@@ -65,8 +65,11 @@
     @issue_custom_fields = IssueCustomField.find(:all, :order => "#{CustomField.table_name}.position")
     @trackers = Tracker.all
     @root_projects = Project.find(:all,
-                                  :conditions => "parent_id IS NULL AND status = #{Project::STATUS_ACTIVE}",
+                                  :conditions => "status = #{Project::STATUS_ACTIVE}",
                                   :order => 'name')
+    if @project != nil
+      @root_projects = @root_projects - @project.fetch_all_subprojects_id_recursively()
+    end
     @project = Project.new(params[:project])
     if request.get?
       @project.identifier = Project.next_identifier if Setting.sequential_project_identifiers?
@@ -108,8 +111,11 @@
 
   def settings
     @root_projects = Project.find(:all,
-                                  :conditions => ["parent_id IS NULL AND status = #{Project::STATUS_ACTIVE} AND id <> ?", @project.id],
+                                  :conditions => ["status = #{Project::STATUS_ACTIVE} AND id <> ?", @project.id],
                                   :order => 'name')
+    if @project != nil
+      @root_projects = @root_projects - @project.fetch_all_subprojects_id_recursively()
+    end
     @issue_custom_fields = IssueCustomField.find(:all, :order => "#{CustomField.table_name}.position")
     @issue_category ||= IssueCategory.new
     @member ||= @project.members.new
diff -bNaur redSVN1797/app/models/project.rb redmine/app/models/project.rb
--- redSVN1797/app/models/project.rb	2008-09-11 16:44:56.446912000 +0200
+++ redmine/app/models/project.rb	2008-09-11 16:27:18.421875000 +0200
@@ -71,10 +71,32 @@
     errors[:identifier].nil? && !(new_record? || identifier.blank?)
   end
   
+  def fetch_all_subprojects_recursively
+    ret = Array.new
+    if self.children.size > 0
+      self.children.each { |subproject|
+        ret << subproject
+        ret += subproject.fetch_all_subprojects_recursively()
+      }
+    end
+    return ret
+  end
+
+  def fetch_all_subprojects_id_recursively
+    ret = Array.new
+    if self.children.size > 0
+      self.children.each { |subproject|
+        ret << subproject.id.to_s
+        ret += subproject.fetch_all_subprojects_id_recursively()
+      }
+    end
+    return ret
+  end
+  
   def issues_with_subprojects(include_subprojects=false)
     conditions = nil
     if include_subprojects
-      ids = [id] + child_ids
+      ids = [id] + fetch_all_subprojects_id_recursively()
       conditions = ["#{Project.table_name}.id IN (#{ids.join(',')}) AND #{Project.visible_by}"]
     end
     conditions ||= ["#{Project.table_name}.id = ?", id]
@@ -247,8 +269,6 @@
 
 protected
   def validate
-    errors.add(parent_id, " must be a root project") if parent and parent.parent
-    errors.add_to_base("A project with subprojects can't be a subproject") if parent and children.size > 0
     errors.add(:identifier, :activerecord_error_invalid) if !identifier.blank? && identifier.match(/^\d*$/)
   end
   
diff -bNaur redSVN1797/app/models/query.rb redmine/app/models/query.rb
--- redSVN1797/app/models/query.rb	2008-09-11 16:44:56.384415200 +0200
+++ redmine/app/models/query.rb	2008-09-11 08:52:04.204289400 +0200
@@ -269,10 +269,10 @@
           # main project only
         else
           # all subprojects
-          ids += project.child_ids
+          ids += project.fetch_all_subprojects_id_recursively()
         end
       elsif Setting.display_subprojects_issues?
-        ids += project.child_ids
+        ids += project.fetch_all_subprojects_id_recursively()
       end
       project_clauses << "#{Issue.table_name}.project_id IN (%s)" % ids.join(',')
     elsif project