diff --git a/OpenSim/Region/Framework/Scenes/SceneGraph.cs b/OpenSim/Region/Framework/Scenes/SceneGraph.cs
index 66fb493551..bc3400a7a5 100644
--- a/OpenSim/Region/Framework/Scenes/SceneGraph.cs
+++ b/OpenSim/Region/Framework/Scenes/SceneGraph.cs
@@ -215,27 +215,9 @@ namespace OpenSim.Region.Framework.Scenes
                 if (sp.IsChildAgent)
                     continue;
 
-                if (sp.ParentID != 0)
-                {
-                    // sitting avatar
-                    SceneObjectPart sop = m_parentScene.GetSceneObjectPart(sp.ParentID);
-                    if (sop != null)
-                    {
-                        coarseLocations.Add(sop.AbsolutePosition + sp.OffsetPosition);
-                        avatarUUIDs.Add(sp.UUID);
-                    }
-                    else
-                    {
-                        // we can't find the parent..  ! arg!
-                        coarseLocations.Add(sp.AbsolutePosition);
-                        avatarUUIDs.Add(sp.UUID);
-                    }
-                }
-                else
-                {
-                    coarseLocations.Add(sp.AbsolutePosition);
-                    avatarUUIDs.Add(sp.UUID);
-                }
+                coarseLocations.Add(sp.AbsolutePosition);
+
+                avatarUUIDs.Add(sp.UUID);
             }
         }
 
diff --git a/OpenSim/Region/Framework/Scenes/ScenePresence.cs b/OpenSim/Region/Framework/Scenes/ScenePresence.cs
index be56fe136c..b84660a1be 100644
--- a/OpenSim/Region/Framework/Scenes/ScenePresence.cs
+++ b/OpenSim/Region/Framework/Scenes/ScenePresence.cs
@@ -432,7 +432,7 @@ namespace OpenSim.Region.Framework.Scenes
         {
             get
             {
-                if (PhysicsActor != null && m_parentID == 0)
+                if (PhysicsActor != null)
                 {
                     m_pos = PhysicsActor.Position;
 
@@ -477,7 +477,7 @@ namespace OpenSim.Region.Framework.Scenes
                     }
                 }
 
-                // Don't update while sitting
+                // Don't update while sitting.  The PhysicsActor above is null whilst sitting.
                 if (ParentID == 0)
                 {
                     m_pos = value;
@@ -504,6 +504,7 @@ namespace OpenSim.Region.Framework.Scenes
                 // There is no offset position when not seated
                 if (ParentID == 0)
                     return;
+
                 m_pos = value;
             }
         }
@@ -562,19 +563,18 @@ namespace OpenSim.Region.Framework.Scenes
 
         public bool IsChildAgent { get; set; }
 
-        public uint ParentID
-        {
-            get { return m_parentID; }
-            set { m_parentID = value; }
-        }
-        private uint m_parentID;
+        /// <summary>
+        /// If the avatar is sitting, the local ID of the prim that it's sitting on.  If not sitting then zero.
+        /// </summary>
+        public uint ParentID { get; set; }
 
-        public SceneObjectPart ParentPart
-        {
-            get { return m_parentPart; }
-            set { m_parentPart = value; }
-        }
-        private SceneObjectPart m_parentPart = null;
+        /// <summary>
+        /// If the avatar is sitting, the prim that it's sitting on.  If not sitting then null.
+        /// </summary>
+        /// <remarks>
+        /// If you use this property then you must take a reference since another thread could set it to null.
+        /// </remarks>
+        public SceneObjectPart ParentPart { get; set; }
 
         public float Health
         {
@@ -2204,23 +2204,16 @@ namespace OpenSim.Region.Framework.Scenes
 //                            "[SCENE PRESENCE]: Sitting {0} at position {1} ({2} + {3}) on part {4} {5} without sit target",
 //                            Name, part.AbsolutePosition, m_pos, ParentPosition, part.Name, part.LocalId);
                 }
+
+                ParentPart = m_scene.GetSceneObjectPart(m_requestedSitTargetID);
+                ParentID = m_requestedSitTargetID;
+
+                Velocity = Vector3.Zero;
+                RemoveFromPhysicalScene();
+        
+                Animator.TrySetMovementAnimation(sitAnimation);
+                SendAvatarDataToAllAgents();
             }
-            else
-            {
-                return;
-            }
-
-            ParentPart = m_scene.GetSceneObjectPart(m_requestedSitTargetID);
-            if (ParentPart == null)
-                return;
-
-            ParentID = m_requestedSitTargetID;
-
-            Velocity = Vector3.Zero;
-            RemoveFromPhysicalScene();
-
-            Animator.TrySetMovementAnimation(sitAnimation);
-            SendAvatarDataToAllAgents();
         }
 
         public void HandleAgentSitOnGround()
diff --git a/OpenSim/Region/RegionCombinerModule/RegionCombinerModule.cs b/OpenSim/Region/RegionCombinerModule/RegionCombinerModule.cs
index 09da97a527..eb633b33bb 100644
--- a/OpenSim/Region/RegionCombinerModule/RegionCombinerModule.cs
+++ b/OpenSim/Region/RegionCombinerModule/RegionCombinerModule.cs
@@ -712,33 +712,16 @@ namespace OpenSim.Region.RegionCombinerModule
 
             List<Vector3> CoarseLocations = new List<Vector3>();
             List<UUID> AvatarUUIDs = new List<UUID>();
+            
             connectiondata.RegionScene.ForEachRootScenePresence(delegate(ScenePresence sp)
             {
                 if (sp.UUID != presence.UUID)
                 {
-                    if (sp.ParentID != 0)
-                    {
-                        // sitting avatar
-                        SceneObjectPart sop = connectiondata.RegionScene.GetSceneObjectPart(sp.ParentID);
-                        if (sop != null)
-                        {
-                            CoarseLocations.Add(sop.AbsolutePosition + sp.AbsolutePosition);
-                            AvatarUUIDs.Add(sp.UUID);
-                        }
-                        else
-                        {
-                            // we can't find the parent..  ! arg!
-                            CoarseLocations.Add(sp.AbsolutePosition);
-                            AvatarUUIDs.Add(sp.UUID);
-                        }
-                    }
-                    else
-                    {
-                        CoarseLocations.Add(sp.AbsolutePosition);
-                        AvatarUUIDs.Add(sp.UUID);
-                    }
+                    CoarseLocations.Add(sp.AbsolutePosition);
+                    AvatarUUIDs.Add(sp.UUID);
                 }
             });
+
             DistributeCourseLocationUpdates(CoarseLocations, AvatarUUIDs, connectiondata, presence);
         }
 
diff --git a/OpenSim/Region/ScriptEngine/Shared/Api/Implementation/LSL_Api.cs b/OpenSim/Region/ScriptEngine/Shared/Api/Implementation/LSL_Api.cs
index 786ae6e6ff..bb374ed002 100644
--- a/OpenSim/Region/ScriptEngine/Shared/Api/Implementation/LSL_Api.cs
+++ b/OpenSim/Region/ScriptEngine/Shared/Api/Implementation/LSL_Api.cs
@@ -3825,7 +3825,8 @@ namespace OpenSim.Region.ScriptEngine.Shared.Api
             List<String> nametable = new List<String>();
             World.ForEachRootScenePresence(delegate(ScenePresence presence)
             {
-                if (presence.ParentID != 0 && m_host.ParentGroup.HasChildPrim(presence.ParentID))
+                SceneObjectPart sitPart = presence.ParentPart;
+                if (sitPart != null && m_host.ParentGroup.HasChildPrim(sitPart.LocalId))
                     nametable.Add(presence.ControllingClient.Name);
             });
 
@@ -4393,22 +4394,11 @@ namespace OpenSim.Region.ScriptEngine.Shared.Api
 
                 // Find pushee position
                 // Pushee Linked?
-                if (pusheeav.ParentID != 0)
-                {
-                    SceneObjectPart parentobj = World.GetSceneObjectPart(pusheeav.ParentID);
-                    if (parentobj != null)
-                    {
-                        PusheePos = parentobj.AbsolutePosition;
-                    }
-                    else
-                    {
-                        PusheePos = pusheeav.AbsolutePosition;
-                    }
-                }
+                SceneObjectPart sitPart = pusheeav.ParentPart;
+                if (sitPart != null)
+                    PusheePos = sitPart.AbsolutePosition;
                 else
-                {
                     PusheePos = pusheeav.AbsolutePosition;
-                }
             }
 
             if (!pusheeIsAvatar)
@@ -5603,7 +5593,7 @@ namespace OpenSim.Region.ScriptEngine.Shared.Api
                     flags |= ScriptBaseClass.AGENT_IN_AIR;
             }
 
-             if (agent.ParentID != 0)
+             if (agent.ParentPart != null)
              {
                  flags |= ScriptBaseClass.AGENT_ON_OBJECT;
                  flags |= ScriptBaseClass.AGENT_SITTING;
@@ -7692,7 +7682,7 @@ namespace OpenSim.Region.ScriptEngine.Shared.Api
             World.ForEachRootScenePresence(delegate(ScenePresence presence)
             {
                 if (presence.ParentID != 0 && m_host.ParentGroup.HasChildPrim(presence.ParentID))
-                        avatarCount++;
+                    avatarCount++;
             });
 
             return m_host.ParentGroup.PrimCount + avatarCount;