diff --git a/app/controllers/tasks_controller.rb b/app/controllers/tasks_controller.rb
--- a/app/controllers/tasks_controller.rb
+++ b/app/controllers/tasks_controller.rb
@@ -8,22 +8,45 @@
 
   def list
     @problems = Problem.find_available_problems
-    @user = User.find(session[:user_id])
   end
 
+  # this has contest-wide access control
   def view
     base_name = params[:file]
-    if !check_user_viewability(base_name)
+    base_filename = File.basename("#{base_name}.#{params[:ext]}")
+    filename = "#{Problem.download_file_basedir}/#{base_filename}"
+
+    if !FileTest.exists?(filename)
       redirect_to :action => 'index' and return
     end
 
-    base_filename = File.basename("#{base_name}.#{params[:ext]}")
-    filename = "#{Problem.download_file_basedir}/#{base_filename}"
+    send_file_to_user(filename, base_filename)
+  end
 
-    if !check_user_viewability(base_name) or !FileTest.exists?(filename)
+  # this has problem-level access control
+  def download
+    problem = Problem.find(params[:id])
+    if !problem or !problem.available or !@user.can_view_problem? problem
       redirect_to :action => 'index' and return
     end
 
+    base_name = params[:file]
+    base_filename = File.basename("#{base_name}.#{params[:ext]}")
+    filename = "#{Problem.download_file_basedir}/#{params[:id]}/#{base_filename}"
+    puts "SENDING: #{filename}"
+
+    if !FileTest.exists?(filename)
+      redirect_to :action => 'index' and return
+    end
+
+    puts "SENDING: #{filename}"
+
+    send_file_to_user(filename, base_filename)
+  end
+
+  protected
+
+  def send_file_to_user(filename, base_filename)
     if defined?(USE_APACHE_XSENDFILE) and USE_APACHE_XSENDFILE
       response.headers['Content-Type'] = "application/force-download" 
       response.headers['Content-Disposition'] = "attachment; filename=\"#{File.basename(filename)}\"" 
@@ -41,8 +64,6 @@
     end
   end
 
-  protected
-
   def check_viewability
     @user = User.find(session[:user_id])
     if @user==nil or !Configuration.show_tasks_to?(@user)
@@ -51,10 +72,4 @@
     end
   end
 
-  def check_user_viewability(filename)
-    # individual file access control shall be added here
-    return false if not @user
-    return Configuration.show_tasks_to?(@user)
-  end
-
 end
diff --git a/app/helpers/main_helper.rb b/app/helpers/main_helper.rb
--- a/app/helpers/main_helper.rb
+++ b/app/helpers/main_helper.rb
@@ -6,7 +6,8 @@
     elsif !problem.description_filename.blank?
       basename, ext = problem.description_filename.split('.')
       options[:controller] = 'tasks'
-      options[:action] = 'view'
+      options[:action] = 'download'
+      options[:id] = problem.id
       options[:file] = basename
       options[:ext] = ext
       return link_to name, options
diff --git a/app/models/user.rb b/app/models/user.rb
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -182,6 +182,29 @@
     end
   end
 
+  def problem_in_user_contests?(problem)
+    problem_contests = problem.contests.all
+
+    if problem_contests.length == 0   # this is public contest
+      return true
+    end
+
+    contests.each do |contest|
+      if problem_contests.find {|c| c.id == contest.id }
+        return true
+      end
+    end
+    return false
+  end
+
+  def can_view_problem?(problem)
+    if not Configuration.multicontests?
+      return problem.available
+    else
+      return problem_in_user_contests? problem
+    end
+  end
+
   protected
     def encrypt_new_password
       return if password.blank?
diff --git a/config/routes.rb b/config/routes.rb
--- a/config/routes.rb
+++ b/config/routes.rb
@@ -23,6 +23,7 @@
   map.connect ':controller/service.wsdl', :action => 'wsdl'
 
   map.connect 'tasks/view/:file.:ext', :controller => 'tasks', :action => 'view'
+  map.connect 'tasks/download/:id/:file.:ext', :controller => 'tasks', :action => 'download'
 
   # Install the default route as the lowest priority.
   map.connect ':controller/:action/:id.:format'
diff --git a/lib/testdata_importer.rb b/lib/testdata_importer.rb
--- a/lib/testdata_importer.rb
+++ b/lib/testdata_importer.rb
@@ -51,10 +51,15 @@
     ext = TestdataImporter.long_ext(tempfile.original_filename)
 
     extract_dir = File.join(GraderScript.raw_dir, @problem.name)
-    begin
-      Dir.mkdir extract_dir
-    rescue Errno::EEXIST
+    if File.exists? extract_dir
+      backup_count = 0
+      begin
+        backup_count += 1
+        backup_dirname = "#{extract_dir}.backup.#{backup_count}"
+      end while File.exists? backup_dirname
+      File.rename(extract_dir, backup_dirname)
     end
+    Dir.mkdir extract_dir
 
     if ext=='.tar.gz' or ext=='.tgz'
       cmd = "tar -zxvf #{testdata_filename} -C #{extract_dir}"
@@ -138,9 +143,23 @@
 
   def import_problem_pdf(dirname)
     pdf_files = Dir["#{dirname}/*.pdf"]
+    puts "CHECKING... #{dirname}"
     if pdf_files.length != 0
+      puts "HAS PDF FILE"
       filename = pdf_files[0]
-      out_filename = "#{Problem.download_file_basedir}/#{@problem.name}.pdf"
+
+      @problem.save if not @problem.id
+      out_dirname = "#{Problem.download_file_basedir}/#{@problem.id}"
+      if not FileTest.exists? out_dirname
+        Dir.mkdir out_dirname
+      end
+
+      out_filename = "#{out_dirname}/#{@problem.name}.pdf"
+
+      if FileTest.exists? out_filename
+        File.delete out_filename
+      end
+
       File.rename(filename, out_filename)
       @problem.description_filename = "#{@problem.name}.pdf"
       @problem.save