This should fix the chunk ghosting bug

src/main/java/org/bukkit/craftbukkit/CraftChunk.java

@@ -36,12 +36,16 @@ public class CraftChunk implements Chunk {
     public net.minecraft.server.Chunk getHandle() {
         net.minecraft.server.Chunk c = weakChunk.get();
         if (c == null) {
-            weakChunk = new WeakReference<net.minecraft.server.Chunk>(worldServer.c(x,z));
-            c = weakChunk.get();
+            c = worldServer.c(x,z);
+            weakChunk = new WeakReference<net.minecraft.server.Chunk>(c);
         }
         return c;
     }
 
+    void breakLink() {
+        weakChunk.clear();
+    } 
+
     public int getX() {
         return x;
     }

src/main/java/org/bukkit/craftbukkit/CraftWorld.java

@@ -45,6 +45,7 @@ public class CraftWorld implements World {
     }
 
     public void preserveChunk( CraftChunk chunk ) {
+        chunk.breakLink();
         unloadedChunks.put( (chunk.getX() << 16) + chunk.getZ(), chunk );
     }
 
@@ -141,6 +142,7 @@ public class CraftWorld implements World {
             provider.a(chunk);
         }
 
+        preserveChunk((CraftChunk)chunk.bukkitChunk);
         provider.a.remove(x, z);
         provider.e.remove(x, z);
         provider.f.remove(chunk);