Index: app/models/time_entry.rb
===================================================================
--- app/models/time_entry.rb	(revision 1524)
+++ app/models/time_entry.rb	(working copy)
@@ -30,8 +30,10 @@
   validates_length_of :comments, :maximum => 255
 
   def after_initialize
-    if new_record?
-      self.activity ||= Enumeration.default('ACTI')
+    if new_record? && !self.activity
+      if activity = Enumeration.default('ACTI')
+        self.activity_id ||= activity.id
+      end
     end
   end