diff -Nur redmine-1.1.0/app/controllers/journals_controller.rb redmine-1.1.0-rollback/app/controllers/journals_controller.rb
--- redmine-1.1.0/app/controllers/journals_controller.rb	2011-01-09 17:05:00.000000000 -0700
+++ redmine-1.1.0-rollback/app/controllers/journals_controller.rb	2011-02-11 17:15:13.829487200 -0700
@@ -16,10 +16,10 @@
 # Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 
 class JournalsController < ApplicationController
-  before_filter :find_journal, :only => [:edit]
+  before_filter :find_journal, :only => [:edit, :rollback]
   before_filter :find_issue, :only => [:new]
   before_filter :find_optional_project, :only => [:index]
-  before_filter :authorize, :only => [:new, :edit]
+  before_filter :authorize, :only => [:new, :edit, :rollback]
   accept_key_auth :index
 
   helper :issues
@@ -67,6 +67,8 @@
   end
   
   def edit
+    (render_403; return false) unless @journal.editable_by?(User.current)
+    
     if request.post?
       @journal.update_attributes(:notes => params[:notes]) if params[:notes]
       @journal.destroy if @journal.details.empty? && @journal.notes.blank?
@@ -77,11 +79,27 @@
       end
     end
   end
+   
+  def rollback
+    (render_403; return false) unless @journal.can_rollback?(User.current)
+    
+    if @journal.rollback
+      flash[:notice] = l(:notice_successful_update)
+    else
+      # can't seem to bring in the helper method 'error_messages_for'
+      # and injecting it into show.rhtml doesn't seem to work, since 
+      # the @issue loses the errors on redirect (due to issue reload)
+      flash[:error] = "<ul>" + @journal.errors.full_messages.map {|msg| "<li>" + ERB::Util.html_escape(msg) + "</li>"}.join + "</ul>"
+    end
+    respond_to do |format|
+      format.html { redirect_to :controller => 'issues', :action => 'show', :id => @journal.journalized_id }
+      format.api  { render_validation_errors(@issue) }
+    end
+  end
   
 private
   def find_journal
     @journal = Journal.find(params[:id])
-    (render_403; return false) unless @journal.editable_by?(User.current)
     @project = @journal.journalized.project
   rescue ActiveRecord::RecordNotFound
     render_404
diff -Nur redmine-1.1.0/app/models/issue.rb redmine-1.1.0-rollback/app/models/issue.rb
--- redmine-1.1.0/app/models/issue.rb	2011-02-11 12:52:05.752402400 -0700
+++ redmine-1.1.0-rollback/app/models/issue.rb	2011-02-11 17:17:51.065874800 -0700
@@ -182,6 +182,11 @@
     end
     issue
   end
+  
+  # parent_id is never set directly, see :after_save
+  def parent_id=(id)
+    @parent_issue = Issue.find_by_id(id)
+  end
 
   def status_id=(sid)
     self.status = nil
@@ -358,6 +363,33 @@
     @current_journal
   end
   
+  # rollback the changes in a journal, the journal is destroyed on success
+  def rollback(journal)
+    # only allow rollback of journal details for the last journal
+    (errors.add_to_base(l(:notice_locking_conflict)); return) if journal != journals.last
+    
+    # avoid the creation of journals during rollback (see 'attachment removed')
+    @rolling_back = true
+    
+    # roll back each change detailed by the journal
+    journal.details.each do |d|
+      case d.property
+        # issue attribute change
+        when 'attr'; send("#{d.prop_key}=", d.old_value)
+        # rollback custom field change
+        when 'cf'; custom_field_values.each {|v| v.value = d.old_value if v.custom_field_id == d.prop_key.to_i}
+        # remove any added attachments (we can't recover removed attachments)
+        when 'attachment'; attachments.each {|v| attachments.delete(v) if v.id == d.prop_key.to_i}
+      end
+    end
+    
+    # allow the creation of journals again
+    remove_instance_variable(:@rolling_back)
+    
+    # destroy the journal once we save the issue changes
+    journal.destroy if save(false)
+  end 
+
   # Return true if the issue is closed, otherwise false
   def closed?
     self.status.is_closed?
@@ -785,6 +817,7 @@
   
   # Callback on attachment deletion
   def attachment_removed(obj)
+    return if @rolling_back
     journal = init_journal(User.current)
     journal.details << JournalDetail.new(:property => 'attachment',
                                          :prop_key => obj.id,
diff -Nur redmine-1.1.0/app/models/journal.rb redmine-1.1.0-rollback/app/models/journal.rb
--- redmine-1.1.0/app/models/journal.rb	2011-01-09 17:05:00.000000000 -0700
+++ redmine-1.1.0-rollback/app/models/journal.rb	2011-02-11 17:10:38.544713600 -0700
@@ -58,6 +58,20 @@
     usr && usr.logged? && (usr.allowed_to?(:edit_issue_notes, project) || (self.user == usr && usr.allowed_to?(:edit_own_issue_notes, project)))
   end
   
+  def can_rollback?(usr = nil)
+    user = usr || User.current
+    editable_by?(user) && (details.empty? || user.allowed_to?(:rollback_issue_notes, project))
+  end
+  
+  # rollback the changes in a journal, the journal is destroyed on success
+  def rollback
+    # we could have details to rollback, so let the issue 
+    # take care of this more complicated task
+    journalized.rollback(self) || 
+    # on failure, collect the error messages from the issue on failure
+      (journalized.errors.each_full {|msg| errors.add_to_base(msg)}; false)
+  end
+  
   def project
     journalized.respond_to?(:project) ? journalized.project : nil
   end
diff -Nur redmine-1.1.0/app/views/issues/_history.rhtml redmine-1.1.0-rollback/app/views/issues/_history.rhtml
--- redmine-1.1.0/app/views/issues/_history.rhtml	2011-02-11 12:52:05.752402400 -0700
+++ redmine-1.1.0-rollback/app/views/issues/_history.rhtml	2011-02-11 17:10:38.560338800 -0700
@@ -2,6 +2,9 @@
 <% for journal in journals %>
   <div id="change-<%= journal.id %>" class="<%= journal.css_classes %>">
     <h4><div class="journal-link"><%= link_to "##{journal.indice}", :anchor => "note-#{journal.indice}" %></div>
+    <% if journal == journals.last && journal.can_rollback? %>
+      <div class="journal-rollback"><%= link_to(image_tag('cancel.png'), {:controller => 'journals', :action => 'rollback', :id => journal}, :confirm => l(:text_are_you_sure), :method => :post, :title => l(:label_rollback)) %>&nbsp;</div>
+    <% end %>
     <%= avatar(journal.user, :size => "24") %>
     <%= content_tag('a', '', :name => "note-#{journal.indice}")%>
 		<%= authoring journal.created_on, journal.user, :label => :label_updated_time_by %></h4>
diff -Nur redmine-1.1.0/config/locales/en.yml redmine-1.1.0-rollback/config/locales/en.yml
--- redmine-1.1.0/config/locales/en.yml	2011-02-11 12:52:05.752402400 -0700
+++ redmine-1.1.0-rollback/config/locales/en.yml	2011-02-11 17:10:38.560338800 -0700
@@ -378,6 +378,7 @@
   permission_add_issue_notes: Add notes
   permission_edit_issue_notes: Edit notes
   permission_edit_own_issue_notes: Edit own notes
+  permission_rollback_issue_notes: Rollback issue notes
   permission_move_issues: Move issues
   permission_delete_issues: Delete issues
   permission_manage_public_queries: Manage public queries
@@ -793,6 +794,7 @@
   label_project_copy_notifications: Send email notifications during the project copy
   label_principal_search: "Search for user or group:"
   label_user_search: "Search for user:"
+  label_rollback: Rollback
   
   button_login: Login
   button_submit: Submit
diff -Nur redmine-1.1.0/lib/redmine.rb redmine-1.1.0-rollback/lib/redmine.rb
--- redmine-1.1.0/lib/redmine.rb	2011-02-11 12:52:05.768027600 -0700
+++ redmine-1.1.0-rollback/lib/redmine.rb	2011-02-11 17:10:38.575964000 -0700
@@ -72,6 +72,7 @@
     map.permission :add_issue_notes, {:issues => [:edit, :update], :journals => [:new]}
     map.permission :edit_issue_notes, {:journals => :edit}, :require => :loggedin
     map.permission :edit_own_issue_notes, {:journals => :edit}, :require => :loggedin
+    map.permission :rollback_issue_notes, {:journals => [:rollback]}
     map.permission :move_issues, {:issue_moves => [:new, :create]}, :require => :loggedin
     map.permission :delete_issues, {:issues => :destroy}, :require => :member
     # Queries
diff -Nur redmine-1.1.0/public/stylesheets/application.css redmine-1.1.0-rollback/public/stylesheets/application.css
--- redmine-1.1.0/public/stylesheets/application.css	2011-02-11 12:52:05.768027600 -0700
+++ redmine-1.1.0-rollback/public/stylesheets/application.css	2011-02-11 15:59:42.537112400 -0700
@@ -938,6 +938,10 @@
 	float: right;
 }
 
+.journal-rollback {
+	float: right;
+}
+
 h2 img { vertical-align:middle; }
 
 .hascontextmenu { cursor: context-menu; }