diff --git a/src/BasicPathFinding.cs b/src/BasicPathFinding.cs
index c556ae4..1488ee0 100644
--- a/src/BasicPathFinding.cs
+++ b/src/BasicPathFinding.cs
@@ -171,9 +171,12 @@ namespace OpenSim.Modules.PathFinding
 
                 if (_env != null)
                 {
-                    _env.LastTimeUsed = (Int32)(DateTime.UtcNow.Subtract(new DateTime(1970, 1, 1))).TotalSeconds;
-                    m_scriptModule.DispatchReply(requestData.ScriptID, 19850, "", requestData.RequestID.ToString());
-                    return;
+                    lock(_env)
+                    {
+                        _env.LastTimeUsed = (Int32)(DateTime.UtcNow.Subtract(new DateTime(1970, 1, 1))).TotalSeconds;
+                        m_scriptModule.DispatchReply(requestData.ScriptID, 19850, "", requestData.RequestID.ToString());
+                        return;
+                    }
                 }
 
                 m_scriptModule.DispatchReply(requestData.ScriptID, 19851, "", requestData.RequestID.ToString());
@@ -192,11 +195,14 @@ namespace OpenSim.Modules.PathFinding
 
                 if (_env != null)
                 {
-                    List<PathNode> _nodes = _env.Nodes.FindAll(X => X.Target == true);
-
-                    foreach (PathNode thisNode in _nodes)
+                    lock(_env)
                     {
-                        thisNode.Target = false;
+                        List<PathNode> _nodes = _env.Nodes.FindAll(X => X.Target == true);
+
+                        foreach (PathNode thisNode in _nodes)
+                        {
+                            thisNode.Target = false;
+                        }
                     }
                 }
             }
@@ -214,30 +220,33 @@ namespace OpenSim.Modules.PathFinding
 
                 if (_env != null)
                 {
-                    if (isTarget == 1)
-                        removeAllTargets(requestData);
-
-                    PathNode _node = _env.Nodes.Find(X => X.PositionX == (int)position.X && X.PositionY == (int)position.Y);
-
-                    if (_node == null)
+                    lock(_env)
                     {
-                        _node = new PathNode((int)position.X, (int)position.Y, false, false);
-                        _env.Nodes.Add(_node);
+                        if (isTarget == 1)
+                            removeAllTargets(requestData);
+
+                        PathNode _node = _env.Nodes.Find(X => X.PositionX == (int)position.X && X.PositionY == (int)position.Y);
+
+                        if (_node == null)
+                        {
+                            _node = new PathNode((int)position.X, (int)position.Y, false, false);
+                            _env.Nodes.Add(_node);
+                        }
+
+                        if (walkable == 1)
+                            _node.Walkable = true;
+
+                        if (walkable == 0)
+                            _node.Walkable = false;
+
+                        if (isTarget == 1)
+                            _node.Target = true;
+
+                        if (isTarget == 0)
+                            _node.Target = false;
+
+                        return;
                     }
-
-                    if (walkable == 1)
-                        _node.Walkable = true;
-
-                    if (walkable == 0)
-                        _node.Walkable = false;
-
-                    if (isTarget == 1)
-                        _node.Target = true;
-
-                    if (isTarget == 0)
-                        _node.Target = false;
-
-                    return;
                 }
 
                 m_scriptModule.DispatchReply(requestData.ScriptID, 19851, "", requestData.RequestID.ToString());
@@ -256,61 +265,64 @@ namespace OpenSim.Modules.PathFinding
 
                 if (_env != null)
                 {
-                    if ((int)start.X == (int)target.X || (int)start.Y == (int)target.Y)
+                    lock(_env)
                     {
-                        if ((int)start.X == (int)target.X && (int)start.Y == (int)target.Y)
+                        if ((int)start.X == (int)target.X || (int)start.Y == (int)target.Y)
                         {
+                            if ((int)start.X == (int)target.X && (int)start.Y == (int)target.Y)
+                            {
+                                m_scriptModule.DispatchReply(requestData.ScriptID, 19850, "", requestData.RequestID.ToString());
+                                return;
+                            }
+
+                            Vector3 _PointA = new Vector3(0, 0, 0);
+                            Vector3 _PointB = new Vector3(0, 0, 0);
+
+                            if ((int)start.X != (int)target.X)
+                            {
+                                if ((int)start.X < (int)target.X)
+                                {
+                                    _PointA = start;
+                                    _PointB = target;
+                                }
+
+                                if ((int)start.X > (int)target.X)
+                                {
+                                    _PointA = target;
+                                    _PointB = start;
+                                }
+
+                                while ((int)_PointA.X != _PointB.X)
+                                {
+                                    setPositionData(requestData, _PointA, walkable, 0);
+                                    _PointA.X = (int)_PointA.X + 1;
+                                }
+                            }
+
+                            if ((int)start.Y != (int)target.Y)
+                            {
+                                if ((int)start.Y < (int)target.Y)
+                                {
+                                    _PointA = start;
+                                    _PointB = target;
+                                }
+
+                                if ((int)start.Y > (int)target.Y)
+                                {
+                                    _PointA = target;
+                                    _PointB = start;
+                                }
+
+                                while ((int)_PointA.Y != _PointB.Y)
+                                {
+                                    setPositionData(requestData, _PointA, walkable, 0);
+                                    _PointA.Y = (int)_PointA.Y + 1;
+                                }
+                            }
+
                             m_scriptModule.DispatchReply(requestData.ScriptID, 19850, "", requestData.RequestID.ToString());
                             return;
                         }
-
-                        Vector3 _PointA = new Vector3(0, 0, 0);
-                        Vector3 _PointB = new Vector3(0, 0, 0);
-
-                        if ((int)start.X != (int)target.X)
-                        {
-                            if ((int)start.X < (int)target.X)
-                            {
-                                _PointA = start;
-                                _PointB = target;
-                            }
-
-                            if ((int)start.X > (int)target.X)
-                            {
-                                _PointA = target;
-                                _PointB = start;
-                            }
-
-                            while ((int)_PointA.X != _PointB.X)
-                            {
-                                setPositionData(requestData, _PointA, walkable, 0);
-                                _PointA.X = (int)_PointA.X + 1;
-                            }
-                        }
-
-                        if ((int)start.Y != (int)target.Y)
-                        {
-                            if ((int)start.Y < (int)target.Y)
-                            {
-                                _PointA = start;
-                                _PointB = target;
-                            }
-
-                            if ((int)start.Y > (int)target.Y)
-                            {
-                                _PointA = target;
-                                _PointB = start;
-                            }
-
-                            while ((int)_PointA.Y != _PointB.Y)
-                            {
-                                setPositionData(requestData, _PointA, walkable, 0);
-                                _PointA.Y = (int)_PointA.Y + 1;
-                            }
-                        }
-
-                        m_scriptModule.DispatchReply(requestData.ScriptID, 19850, "", requestData.RequestID.ToString());
-                        return;
                     }
                 }
                 else