diff --git a/Commands/building/CmdMark.cs b/Commands/building/CmdMark.cs
index 20b5c20af..ed9507336 100644
--- a/Commands/building/CmdMark.cs
+++ b/Commands/building/CmdMark.cs
@@ -37,7 +37,7 @@ namespace MCGalaxy.Commands.Building {
             if (!p.HasBlockchange) {
                 Player.Message(p, "Cannot mark, no selection or cuboid in progress."); return;
             }
-            p.ManualChange(P.X, P.Y, P.Z, 0, Block.rock);
+            p.ManualChange(P.X, P.Y, P.Z, 0, Block.rock, 0, false);
             Player.Message(p, "Mark placed at &b({0}, {1}, {2})", P.X, P.Y, P.Z);
         }
         
diff --git a/Commands/other/CmdC4.cs b/Commands/other/CmdC4.cs
index 86e4d442f..90d09b6a4 100644
--- a/Commands/other/CmdC4.cs
+++ b/Commands/other/CmdC4.cs
@@ -46,11 +46,11 @@ namespace MCGalaxy.Commands
         void Blockchange1(Player p, ushort x, ushort y, ushort z, byte type, byte extType) {
             p.ClearBlockchange();
             if (type == Block.red) {
-                p.ManualChange(x, y, z, 1, Block.c4det, 0);
+                p.ManualChange(x, y, z, 1, Block.c4det);
                 Player.Message(p, "Placed detonator block!");
                 return;
             } else if (type != Block.air) {
-                p.ManualChange(x, y, z, 1, Block.c4, 0);
+                p.ManualChange(x, y, z, 1, Block.c4);
             }
             p.Blockchange += new Player.BlockchangeEventHandler(Blockchange1);
         }
diff --git a/Player/Group/Group.cs b/Player/Group/Group.cs
index e18735597..716f27bf3 100644
--- a/Player/Group/Group.cs
+++ b/Player/Group/Group.cs
@@ -114,6 +114,7 @@ namespace MCGalaxy
 
         public static List<Group> GroupList = new List<Group>();
         public static Group standard;
+        static readonly object saveLock = new object();
         
         /// <summary> Load up all server groups </summary>
         public static void InitAll() {
@@ -146,9 +147,10 @@ namespace MCGalaxy
         /// <summary> Save givenList group </summary>
         /// <param name="givenList">The list of groups to save</param>
         public static void saveGroups(List<Group> givenList) {
-            GroupProperties.SaveGroups(givenList);
-            if (OnGroupSave != null)
-                OnGroupSave();
+        	lock (saveLock)
+        	    GroupProperties.SaveGroups(givenList);
+        	
+            if (OnGroupSave != null) OnGroupSave();
             OnGroupSaveEvent.Call();
         }
         
diff --git a/Player/Group/GroupCommands.cs b/Player/Group/GroupCommands.cs
index 11138dbe4..1649c843f 100644
--- a/Player/Group/GroupCommands.cs
+++ b/Player/Group/GroupCommands.cs
@@ -129,7 +129,13 @@ namespace MCGalaxy {
             }
         }
 
+        static readonly object saveLock = new object();
         public static void Save(List<rankAllowance> givenList) {
+            lock (saveLock)
+                SaveCore(givenList);
+        }
+        
+        static void SaveCore(List<rankAllowance> givenList) {
             try {
                 using (StreamWriter w = new StreamWriter("properties/command.properties")) {
                     w.WriteLine("#Version 2");
diff --git a/Player/Player.Handlers.cs b/Player/Player.Handlers.cs
index 52d8963e9..64a22ba0a 100644
--- a/Player/Player.Handlers.cs
+++ b/Player/Player.Handlers.cs
@@ -45,6 +45,11 @@ namespace MCGalaxy {
         }
         
         public void ManualChange(ushort x, ushort y, ushort z, byte action, byte type, byte extType = 0) {
+        	ManualChange(x, y, z, action, type, extType, true);
+        }
+        
+        public void ManualChange(ushort x, ushort y, ushort z, byte action, 
+                                 byte type, byte extType, bool checkPlaceDist) {
             byte b = level.GetTile(x, y, z);
             if ( b == Block.Zero ) { return; }
             if ( jailed || !agreed ) { RevertBlock(x, y, z); return; }
@@ -91,12 +96,12 @@ namespace MCGalaxy {
             OnBlockChangeEvent.Call(this, x, y, z, type, extType);
             if ( cancelBlock ) { cancelBlock = false; return; }
 
-            if ( group.Permission == LevelPermission.Banned ) return;
-            if ( group.Permission == LevelPermission.Guest ) {
-                int Diff = Math.Abs((pos[0] / 32) - x) + Math.Abs((pos[1] / 32) - y) 
-                    + Math.Abs((pos[2] / 32) - z);
+            if (group.Permission == LevelPermission.Banned) return;
+            if (checkPlaceDist && group.Permission == LevelPermission.Guest) {
+            	int Diff = Math.Abs(((short)pos[0] / 32) - x) + Math.Abs(((short)pos[1] / 32) - y) 
+            	    + Math.Abs(((short)pos[2] / 32) - z);
 
-                if ((Diff > ReachDistance + 4) && !(lastCMD == "click" || lastCMD == "mark")) {
+                if (Diff > ReachDistance + 4) {
                     Server.s.Log(name + " attempted to build with a " + Diff + " distance offset");
                     SendMessage("You can't build that far away.");
                     RevertBlock(x, y, z); return;