diff --git a/src/Gui/Gui.cs b/src/Gui/Gui.cs
index 6121d8f..e9f345a 100644
--- a/src/Gui/Gui.cs
+++ b/src/Gui/Gui.cs
@@ -52,7 +52,9 @@ namespace WorldOfPeacecraft
 		{
 			BufferedGraphics buffer = BufferedGraphicsManager.Current.Allocate (Board.CreateGraphics (), Board.DisplayRectangle);
 			Graphics g = buffer.Graphics;
-			PaintMap(g);
+			lock (Backend) {
+				PaintMap (g);
+			}
 			buffer.Render();
 		}
 
diff --git a/src/Parser.cs b/src/Parser.cs
index 5524a24..87aa864 100644
--- a/src/Parser.cs
+++ b/src/Parser.cs
@@ -172,11 +172,15 @@ namespace WorldOfPeacecraft
 			switch (block.GetName ()) {
 			case MessPlayer:
 				Player player = MapPlayer (block);
-				Backend.removePlayer (player);
+				lock (Backend) {
+					Backend.removePlayer (player);
+				}
 				break;
 			case MessDragon:
 				Dragon dragon = MapDragon (block);
-				Backend.removeDragon (dragon);
+				lock (Backend) {
+					Backend.removeDragon (dragon);
+				}
 				break;
 			default:
 				ThrowUnknownBlockException(deleteBlock, block);
@@ -199,7 +203,9 @@ namespace WorldOfPeacecraft
 			foreach (Block cell in cellsBlock.GetBlocks()) {
 				map.SetTile(MapMapcell(cell));
 			}
-			Backend.SetMap(map);
+			lock (Backend) {
+				Backend.SetMap (map);
+			}
 			Backend.RefreshGui();
 		}
 
@@ -279,12 +285,17 @@ namespace WorldOfPeacecraft
 
 		private void ProcessPlayer (Block playerBlock)
 		{
-			Backend.SetPlayer(MapPlayer(playerBlock));
+			lock (Backend) {
+				Backend.SetPlayer (MapPlayer (playerBlock));
+			}
 		}
 		
 		private void ProcessMapcell (Block mapcellBlock)
 		{
-			Backend.getMapObject().SetTile(MapMapcell(mapcellBlock));
+			Tile tile = MapMapcell (mapcellBlock);
+			lock (Backend) {
+				 Backend.getMapObject ().SetTile (tile);
+			}
 		}
 
 		private void ProcessYourid (Block yourIdBlock)
@@ -313,34 +324,46 @@ namespace WorldOfPeacecraft
 
 		private void ProcessEntities (Block entitiesBlock)
 		{
-			Backend.clearDragons ();
-			Backend.clearPlayers ();
-			foreach (Block entityBlock in entitiesBlock.GetBlocks ()) {
-				switch (entityBlock.GetName()) {
-				case MessPlayer:
-					Backend.SetPlayer(MapPlayer(entityBlock));
-					break;
-				case MessDragon:
-					Backend.SetDragon(MapDragon(entityBlock));
-					break;
-				default:
-					ThrowUnknownBlockException(entitiesBlock, entityBlock);
-					break;
+			// This lock can be placed more efficiently. Does it make sense?
+			lock (Backend) {
+				Backend.clearDragons ();
+				Backend.clearPlayers ();
+				foreach (Block entityBlock in entitiesBlock.GetBlocks ()) {
+					switch (entityBlock.GetName ()) {
+					case MessPlayer:
+						lock (Backend) {
+							Backend.SetPlayer (MapPlayer (entityBlock));
+						}
+						break;
+					case MessDragon:
+						Backend.SetDragon (MapDragon (entityBlock));
+						break;
+					default:
+						ThrowUnknownBlockException (entitiesBlock, entityBlock);
+						break;
+					}
 				}
+				Backend.RefreshGui();
 			}
 		}
 
 		private void ProcessPlayers (Block playersBlock)
 		{
-			Backend.clearPlayers ();
-			foreach (Block playerBlock in playersBlock.GetBlocks ()) {
-				Backend.SetPlayer(MapPlayer(playerBlock));
+			// This lock can be placed more efficiently. Does it make sense?
+			lock (Backend) {
+				Backend.clearPlayers ();
+				foreach (Block playerBlock in playersBlock.GetBlocks ()) {
+					Backend.SetPlayer (MapPlayer (playerBlock));
+				}
 			}
 		}
 
 		private void ProcessDragon (Block dragonBlock)
 		{
-			Backend.SetDragon(MapDragon(dragonBlock));
+			Dragon dragon = MapDragon (dragonBlock);
+			lock (Backend) {
+				Backend.SetDragon (dragon);
+			}
 		}
 
 		private Dragon MapDragon (Block dragonBlock)