diff --git a/mozilla/embedding/components/windowwatcher/src/nsWindowWatcher.cpp b/mozilla/embedding/components/windowwatcher/src/nsWindowWatcher.cpp
index 3f95fa5ebf3..bf944bafc9f 100644
--- a/mozilla/embedding/components/windowwatcher/src/nsWindowWatcher.cpp
+++ b/mozilla/embedding/components/windowwatcher/src/nsWindowWatcher.cpp
@@ -609,12 +609,13 @@ nsWindowWatcher::OpenWindowJS(nsIDOMWindow *aParent,
 
     if (weAreModal) {
       rv = queueGuard.Push();
-      if (NS_SUCCEEDED(rv)) {
-        windowIsModal = PR_TRUE;
-        // in case we added this because weAreModal
-        chromeFlags |= nsIWebBrowserChrome::CHROME_MODAL |
-          nsIWebBrowserChrome::CHROME_DEPENDENT;
-      }
+      if (NS_FAILED(rv))
+        return rv;
+
+      windowIsModal = PR_TRUE;
+      // in case we added this because weAreModal
+      chromeFlags |= nsIWebBrowserChrome::CHROME_MODAL |
+                     nsIWebBrowserChrome::CHROME_DEPENDENT;
     }
 
     NS_ASSERTION(mWindowCreator,
diff --git a/mozilla/xpcom/threads/nsEventQueue.cpp b/mozilla/xpcom/threads/nsEventQueue.cpp
index 6d375e7eef8..0d9a29c3bec 100644
--- a/mozilla/xpcom/threads/nsEventQueue.cpp
+++ b/mozilla/xpcom/threads/nsEventQueue.cpp
@@ -62,6 +62,8 @@ static PLEventQueue *gEventQueueLogQueue = 0;
 static PRThread *gEventQueueLogThread = 0;
 #endif
 
+#define MAX_EVENTQUEUE_NESTING_DEPTH 12
+
 // in a real system, these would be members in a header class...
 static const char gActivatedNotification[] = "nsIEventQueueActivated";
 static const char gDestroyedNotification[] = "nsIEventQueueDestroyed";
@@ -539,26 +541,32 @@ nsEventQueueImpl::AppendQueue(nsIEventQueue *aQueue)
 */
   rv = NS_ERROR_NO_INTERFACE;
 
-#ifdef NS_DEBUG
-  int depth = 0;
-  nsEventQueueImpl *next = this;
-  while (next && depth < 100) {
-    next = NS_STATIC_CAST(nsEventQueueImpl *, next->mYoungerQueue);
-    ++depth;
-  }
-  if (depth > 5) {
-    char warning[80];
-    PR_snprintf(warning, sizeof(warning),
-      "event queue chain length is %d. this is almost certainly a leak.", depth);
-    NS_WARNING(warning);
-  }
-#endif
-
-  // (be careful doing this outside nsEventQueueService's mEventQMonitor)
-
   GetYoungest(getter_AddRefs(end));
   nsCOMPtr<nsPIEventQueueChain> endChain(do_QueryInterface(end));
+  
+  // (be careful doing this outside nsEventQueueService's mEventQMonitor)
+
   if (endChain) {
+    int depth = 0;
+    nsCOMPtr<nsPIEventQueueChain> chain = endChain;
+    while (chain) {
+      nsCOMPtr<nsIEventQueue> q;
+      chain->GetElder(getter_AddRefs(q));
+      chain = do_QueryInterface(q);
+      ++depth;
+      if (depth > MAX_EVENTQUEUE_NESTING_DEPTH)
+        return NS_ERROR_FAILURE;
+    }
+  
+#ifdef NS_DEBUG
+    if (depth > 5) {
+      char warning[80];
+      PR_snprintf(warning, sizeof(warning),
+        "event queue chain length is %d. this is almost certainly a leak.", depth);
+      NS_WARNING(warning);
+    }
+#endif
+
     endChain->SetYounger(queueChain);
     queueChain->SetElder(endChain);
     rv = NS_OK;
@@ -643,7 +651,7 @@ nsEventQueueImpl::GetYounger(nsIEventQueue **aQueue)
     *aQueue = nsnull;
     return NS_OK;
   }
-  return mYoungerQueue->QueryInterface(NS_GET_IID(nsIEventQueue), (void**)&aQueue);
+  return CallQueryInterface(mYoungerQueue, aQueue);
 }
 
 NS_IMETHODIMP
@@ -653,7 +661,7 @@ nsEventQueueImpl::GetElder(nsIEventQueue **aQueue)
     *aQueue = nsnull;
     return NS_OK;
   }
-  return mElderQueue->QueryInterface(NS_GET_IID(nsIEventQueue), (void**)&aQueue);
+  return CallQueryInterface(mElderQueue, aQueue);
 }
 
 NS_IMETHODIMP
diff --git a/mozilla/xpcom/threads/nsEventQueueService.cpp b/mozilla/xpcom/threads/nsEventQueueService.cpp
index 6b16002e28e..6551e7c03e6 100644
--- a/mozilla/xpcom/threads/nsEventQueueService.cpp
+++ b/mozilla/xpcom/threads/nsEventQueueService.cpp
@@ -296,20 +296,24 @@ nsEventQueueServiceImpl::PushThreadEventQueue(nsIEventQueue **aNewQueue)
       mEventQTable.Put(currentThread, newQueue);
     }
 
-      // append to the event queue chain -- QI the queue in the hash table
-      nsCOMPtr<nsPIEventQueueChain> ourChain(do_QueryInterface(queue));
+    // append to the event queue chain -- QI the queue in the hash table
+    nsCOMPtr<nsPIEventQueueChain> ourChain(do_QueryInterface(queue));
     if (ourChain)
-      ourChain->AppendQueue(newQueue); // append new queue to it
+      rv = ourChain->AppendQueue(newQueue); // append new queue to it
 
-    *aNewQueue = newQueue;
+    if (NS_FAILED(rv)) {
+      NS_RELEASE(newQueue);
+    } else {
+      *aNewQueue = newQueue;
 
 #if defined(PR_LOGGING) && defined(DEBUG_danm)
-    PLEventQueue *equeue;
-    (*aNewQueue)->GetPLEventQueue(&equeue);
-    PR_LOG(gEventQueueLog, PR_LOG_DEBUG,
-           ("EventQueue: Service push queue [queue=%lx]",(long)equeue));
-    ++gEventQueueLogCount;
+      PLEventQueue *equeue;
+      (*aNewQueue)->GetPLEventQueue(&equeue);
+      PR_LOG(gEventQueueLog, PR_LOG_DEBUG,
+             ("EventQueue: Service push queue [queue=%lx]",(long)equeue));
+      ++gEventQueueLogCount;
 #endif
+    }
   }
 
   // Release the EventQ lock...