renamed ScenePresence.SendFullUpdateToAllClients() to SendInitialFullUpdateToAllClients(), and added a replacement SendFullUpdateToAllClients() method. As the old one (now "Initial") has extra steps in it for sending initial updates/date, Not only was this leading to a lot more data being sent than needed to be, every time it was called. It also seems to have been causing the "other Avatars rotating when you sit down" bug.

OpenSim/Region/Environment/Scenes/ScenePresence.cs

@@ -1626,7 +1626,7 @@ namespace OpenSim.Region.Environment.Scenes
         /// <summary>
         /// Tell *ALL* agents about this agent
         /// </summary>
-        public void SendFullUpdateToAllClients()
+        public void SendInitialFullUpdateToAllClients()
         {
             m_perfMonMS = System.Environment.TickCount;
 
@@ -1648,6 +1648,21 @@ namespace OpenSim.Region.Environment.Scenes
             m_scene.AddAgentTime(System.Environment.TickCount - m_perfMonMS);
         }
 
+        public void SendFullUpdateToAllClients()
+        {
+            m_perfMonMS = System.Environment.TickCount;
+
+            List<ScenePresence> avatars = m_scene.GetScenePresences();
+            foreach (ScenePresence avatar in avatars)
+            {
+                SendFullUpdateToOtherClient(avatar);
+
+            }
+            m_scene.AddAgentUpdates(avatars.Count);
+            m_scene.AddAgentTime(System.Environment.TickCount - m_perfMonMS);
+        }
+
+
         /// <summary>
         /// Do everything required once a client completes its movement into a region 
         /// </summary>
@@ -1664,7 +1679,7 @@ namespace OpenSim.Region.Environment.Scenes
                 m_scene.InformClientOfNeighbours(this);
             }
 
-            SendFullUpdateToAllClients();
+            SendInitialFullUpdateToAllClients();
             SendAppearanceToAllOtherAgents();
          }