--- old/src/macosx/classes/sun/lwawt/LWWindowPeer.java	2013-09-04 12:42:13.408343000 +0400
+++ new/src/macosx/classes/sun/lwawt/LWWindowPeer.java	2013-09-04 12:42:13.236742700 +0400
@@ -81,9 +81,10 @@
     // check that the mouse is over the window
     private volatile boolean isMouseOver = false;
 
+    private static final Object lastCommonMouseEventPeerLock = new Object();
     // A peer where the last mouse event came to. Used by cursor manager to
     // find the component under cursor
-    private static volatile LWComponentPeer lastCommonMouseEventPeer = null;
+    private static LWComponentPeer lastCommonMouseEventPeer = null;
 
     // A peer where the last mouse event came to. Used to generate
     // MOUSE_ENTERED/EXITED notifications
@@ -710,9 +711,7 @@
                 // Sometimes we may get MOUSE_EXITED after lastCommonMouseEventPeer is switched
                 // to a peer from another window. So we must first check if this peer is
                 // the same as lastWindowPeer
-                if (lastCommonMouseEventPeer != null && lastCommonMouseEventPeer.getWindowPeerOrSelf() == this) {
-                    lastCommonMouseEventPeer = null;
-                }
+                cleanLastCommonMouseEventPeer(this);
                 lastMouseEventPeer = null;
             }
         } else if(id == MouseEvent.MOUSE_ENTERED) {
@@ -724,7 +723,7 @@
                     postMouseEnteredEvent(target, when, modifiers, lp,
                             screenX, screenY, clickCount, popupTrigger, button);
                 }
-                lastCommonMouseEventPeer = targetPeer;
+                setLastCommonMouseEventPeer(targetPeer);
                 lastMouseEventPeer = targetPeer;
             }
         } else {
@@ -853,7 +852,7 @@
             postMouseExitedEvent(target, when, modifiers, oldp, screenX, screenY,
                     clickCount, popupTrigger, button);
         }
-        lastCommonMouseEventPeer = targetPeer;
+        setLastCommonMouseEventPeer(targetPeer);
         lastMouseEventPeer = targetPeer;
 
         // Generate Mouse Enter for components
@@ -1111,11 +1110,31 @@
     }
 
     public static LWWindowPeer getWindowUnderCursor() {
-        return lastCommonMouseEventPeer != null ? lastCommonMouseEventPeer.getWindowPeerOrSelf() : null;
+        synchronized (lastCommonMouseEventPeerLock) {
+            return lastCommonMouseEventPeer != null ? lastCommonMouseEventPeer.getWindowPeerOrSelf() : null;
+        }
     }
 
     public static LWComponentPeer<?, ?> getPeerUnderCursor() {
-        return lastCommonMouseEventPeer;
+        synchronized (lastCommonMouseEventPeerLock) {
+            return lastCommonMouseEventPeer;
+        }
+    }
+
+    static boolean cleanLastCommonMouseEventPeer(LWWindowPeer previous) {
+        synchronized (lastCommonMouseEventPeerLock) {
+            if (lastCommonMouseEventPeer != null && lastCommonMouseEventPeer.getWindowPeerOrSelf() == previous) {
+                lastCommonMouseEventPeer = null;
+                return true;
+            }
+            return false;
+        }
+    }
+
+    static void setLastCommonMouseEventPeer(LWComponentPeer<?, ?> newValue) {
+        synchronized (lastCommonMouseEventPeerLock) {
+            lastCommonMouseEventPeer = newValue;
+        }
     }
 
     /*