diff --git a/OpenSim/Region/CoreModules/Agent/AssetTransaction/AgentAssetsTransactions.cs b/OpenSim/Region/CoreModules/Agent/AssetTransaction/AgentAssetsTransactions.cs
index 0271738aee..f56d17d108 100644
--- a/OpenSim/Region/CoreModules/Agent/AssetTransaction/AgentAssetsTransactions.cs
+++ b/OpenSim/Region/CoreModules/Agent/AssetTransaction/AgentAssetsTransactions.cs
@@ -33,6 +33,7 @@ using OpenSim.Framework;
 
 using OpenSim.Region.Framework.Scenes;
 using OpenSim.Services.Interfaces;
+using OpenSim.Region.Framework.Interfaces;
 
 namespace OpenSim.Region.CoreModules.Agent.AssetTransaction
 {
@@ -119,6 +120,14 @@ namespace OpenSim.Region.CoreModules.Agent.AssetTransaction
             }
             else
             {
+                // Check if the xfer is a terrain xfer
+                IEstateModule estateModule = m_Scene.RequestModuleInterface<IEstateModule>();
+                if (estateModule != null)
+                {
+                    if (estateModule.IsTerrainXfer(xferID))
+                        return;
+                }
+                
                 m_log.ErrorFormat(
                     "[AGENT ASSET TRANSACTIONS]: Could not find uploader for xfer id {0}, packet id {1}, data length {2}",
                     xferID, packetID, data.Length);
diff --git a/OpenSim/Region/CoreModules/World/Estate/EstateManagementModule.cs b/OpenSim/Region/CoreModules/World/Estate/EstateManagementModule.cs
index 42db1cf475..17387da751 100644
--- a/OpenSim/Region/CoreModules/World/Estate/EstateManagementModule.cs
+++ b/OpenSim/Region/CoreModules/World/Estate/EstateManagementModule.cs
@@ -829,26 +829,23 @@ namespace OpenSim.Region.CoreModules.World.Estate
         
         private void AbortTerrainXferHandler(IClientAPI remoteClient, ulong XferID)
         {
-            if (TerrainUploader != null)
+            lock (this)
             {
-                lock (TerrainUploader)
+                if ((TerrainUploader != null) && (XferID == TerrainUploader.XferID))
                 {
-                    if (XferID == TerrainUploader.XferID)
-                    {
-                        remoteClient.OnXferReceive -= TerrainUploader.XferReceive;
-                        remoteClient.OnAbortXfer -= AbortTerrainXferHandler;
-                        TerrainUploader.TerrainUploadDone -= HandleTerrainApplication;
+                    remoteClient.OnXferReceive -= TerrainUploader.XferReceive;
+                    remoteClient.OnAbortXfer -= AbortTerrainXferHandler;
+                    TerrainUploader.TerrainUploadDone -= HandleTerrainApplication;
 
-                        TerrainUploader = null;
-                        remoteClient.SendAlertMessage("Terrain Upload aborted by the client");
-                    }
+                    TerrainUploader = null;
+                    remoteClient.SendAlertMessage("Terrain Upload aborted by the client");
                 }
             }
-
         }
+
         private void HandleTerrainApplication(string filename, byte[] terrainData, IClientAPI remoteClient)
         {
-            lock (TerrainUploader)
+            lock (this)
             {
                 remoteClient.OnXferReceive -= TerrainUploader.XferReceive;
                 remoteClient.OnAbortXfer -= AbortTerrainXferHandler;
@@ -907,22 +904,32 @@ namespace OpenSim.Region.CoreModules.World.Estate
 
         private void handleUploadTerrain(IClientAPI remote_client, string clientFileName)
         {
-            if (TerrainUploader == null)
+            lock (this)
             {
-
-                TerrainUploader = new EstateTerrainXferHandler(remote_client, clientFileName);
-                lock (TerrainUploader)
+                if (TerrainUploader == null)
                 {
+                    m_log.DebugFormat("Starting to receive uploaded terrain");
+                    TerrainUploader = new EstateTerrainXferHandler(remote_client, clientFileName);
                     remote_client.OnXferReceive += TerrainUploader.XferReceive;
                     remote_client.OnAbortXfer += AbortTerrainXferHandler;
                     TerrainUploader.TerrainUploadDone += HandleTerrainApplication;
+                    TerrainUploader.RequestStartXfer(remote_client);
+                }
+                else
+                {
+                    remote_client.SendAlertMessage("Another Terrain Upload is in progress.  Please wait your turn!");
                 }
-                TerrainUploader.RequestStartXfer(remote_client);
-
             }
-            else
+        }
+
+        public bool IsTerrainXfer(ulong xferID)
+        {
+            lock (this)
             {
-                remote_client.SendAlertMessage("Another Terrain Upload is in progress.  Please wait your turn!");
+                if (TerrainUploader == null)
+                    return false;
+                else
+                    return TerrainUploader.XferID == xferID;
             }
         }
         
diff --git a/OpenSim/Region/CoreModules/World/Estate/EstateTerrainXferHandler.cs b/OpenSim/Region/CoreModules/World/Estate/EstateTerrainXferHandler.cs
index b8d8b10068..2d74eaf929 100644
--- a/OpenSim/Region/CoreModules/World/Estate/EstateTerrainXferHandler.cs
+++ b/OpenSim/Region/CoreModules/World/Estate/EstateTerrainXferHandler.cs
@@ -78,7 +78,10 @@ namespace OpenSim.Region.CoreModules.World.Estate
         /// <param name="data"></param>
         public void XferReceive(IClientAPI remoteClient, ulong xferID, uint packetID, byte[] data)
         {
-            if (mXferID == xferID)
+            if (mXferID != xferID)
+                return;
+
+            lock (this)
             {
                 if (m_asset.Data.Length > 1)
                 {
@@ -99,7 +102,6 @@ namespace OpenSim.Region.CoreModules.World.Estate
                 if ((packetID & 0x80000000) != 0)
                 {
                     SendCompleteMessage(remoteClient);
-
                 }
             }
         }
diff --git a/OpenSim/Region/Framework/Interfaces/IEstateModule.cs b/OpenSim/Region/Framework/Interfaces/IEstateModule.cs
index d49b24ec0d..944c66b9a6 100644
--- a/OpenSim/Region/Framework/Interfaces/IEstateModule.cs
+++ b/OpenSim/Region/Framework/Interfaces/IEstateModule.cs
@@ -54,5 +54,10 @@ namespace OpenSim.Region.Framework.Interfaces
 
         void setEstateTerrainBaseTexture(int level, UUID texture);
         void setEstateTerrainTextureHeights(int corner, float lowValue, float highValue);
+
+        /// <summary>
+        /// Returns whether the transfer ID is being used for a terrain transfer.
+        /// </summary>
+        bool IsTerrainXfer(ulong xferID);
     }
 }