diff --git a/app/controllers/comments_controller.rb b/app/controllers/comments_controller.rb
index 1efbc9c48..8a64918ae 100644
--- a/app/controllers/comments_controller.rb
+++ b/app/controllers/comments_controller.rb
@@ -50,11 +50,15 @@ class CommentsController < ApplicationController
       # # ������ض�̬�ļ�¼add end
       flash[:notice] = l(:label_comment_added)
       course_activity = CourseActivity.where("course_act_type='News' and course_act_id =#{@news.id}").first
-      course_activity.updated_at = Time.now
-      course_activity.save
+      if course_activity
+        course_activity.updated_at = Time.now
+        course_activity.save
+      end
       user_activity = UserActivity.where("act_type='News' and act_id =#{@news.id}").first
-      user_activity.updated_at = Time.now
-      user_activity.save
+      if user_activity
+        user_activity.updated_at = Time.now
+        user_activity.save
+      end
     end
 
     if params[:user_activity_id]
diff --git a/app/controllers/messages_controller.rb b/app/controllers/messages_controller.rb
index c6ac8b906..4f3f3ec0d 100644
--- a/app/controllers/messages_controller.rb
+++ b/app/controllers/messages_controller.rb
@@ -163,11 +163,15 @@ class MessagesController < ApplicationController
     # @reply.reply_id = params[:id]
     @topic.children << @reply
     course_activity = CourseActivity.where("course_act_type='Message' and course_act_id =#{@topic.id}").first
-    course_activity.updated_at = Time.now
-    course_activity.save
+    if course_activity
+      course_activity.updated_at = Time.now
+      course_activity.save
+    end
     user_activity = UserActivity.where("act_type='Message' and act_id =#{@topic.id}").first
-    user_activity.updated_at = Time.now
-    user_activity.save
+    if user_activity
+      user_activity.updated_at = Time.now
+      user_activity.save
+    end
     #@topic.update_attribute(:updated_on, Time.now)
     if !@reply.new_record?
       if params[:asset_id]
diff --git a/app/controllers/student_work_controller.rb b/app/controllers/student_work_controller.rb
index d39d8fe3b..f2858d097 100644
--- a/app/controllers/student_work_controller.rb
+++ b/app/controllers/student_work_controller.rb
@@ -174,11 +174,15 @@ class StudentWorkController < ApplicationController
 
       if student_work.save
         course_activity = CourseActivity.where("course_act_type='HomeworkCommon' and course_act_id =#{@homework.id}").first
-        course_activity.updated_at = Time.now
-        course_activity.save
+        if course_activity
+          course_activity.updated_at = Time.now
+          course_activity.save
+        end
         user_activity = UserActivity.where("act_type='HomeworkCommon' and act_id =#{@homework.id}").first
-        user_activity.updated_at = Time.now
-        user_activity.save
+        if user_activity
+          user_activity.updated_at = Time.now
+          user_activity.save
+        end
         respond_to do |format|
           format.html {
             flash[:notice] = l(:notice_successful_create)
diff --git a/app/controllers/words_controller.rb b/app/controllers/words_controller.rb
index a0ce8d18e..a59f507df 100644
--- a/app/controllers/words_controller.rb
+++ b/app/controllers/words_controller.rb
@@ -55,12 +55,16 @@ class WordsController < ApplicationController
     @jfm = add_reply_adapter options
     @save_succ = true if @jfm.errors.empty?
     if @save_succ
-    course_activity = CourseActivity.where("course_act_type='JournalsForMessage' and course_act_id =#{parent_id}").first
-    course_activity.updated_at = Time.now
-    course_activity.save
-    user_activity = UserActivity.where("act_type='JournalsForMessage' and act_id =#{parent_id}").first
-    user_activity.updated_at = Time.now
-    user_activity.save
+      course_activity = CourseActivity.where("course_act_type='JournalsForMessage' and course_act_id =#{parent_id}").first
+      if course_activity
+        course_activity.updated_at = Time.now
+        course_activity.save
+      end
+      user_activity = UserActivity.where("act_type='JournalsForMessage' and act_id =#{parent_id}").first
+      if user_activity
+        user_activity.updated_at = Time.now
+        user_activity.save
+      end
     end
     respond_to do |format|
       # format.html {