diff --git a/mozilla/content/xul/document/src/nsXULControllers.cpp b/mozilla/content/xul/document/src/nsXULControllers.cpp
index dd7532aa725..a2aedeca330 100644
--- a/mozilla/content/xul/document/src/nsXULControllers.cpp
+++ b/mozilla/content/xul/document/src/nsXULControllers.cpp
@@ -97,9 +97,7 @@ nsXULControllers::GetControllerForCommand(const PRUnichar *command, nsIControlle
     mControllers->Count(&count);
     for(PRUint32 i=0; i < count; i++) {
         nsCOMPtr<nsIController> controller;
-        nsCOMPtr<nsISupports>   supports;
-        mControllers->GetElementAt(i, getter_AddRefs(supports));
-        controller = do_QueryInterface(supports);
+        mControllers->QueryElementAt(i, NS_GET_IID(nsIController), getter_AddRefs(controller));
         if( controller ) {
             PRBool supportsCommand;
             controller->SupportsCommand(command, &supportsCommand);
@@ -130,14 +128,9 @@ NS_IMETHODIMP
 nsXULControllers::RemoveControllerAt(PRUint32 index, nsIController **_retval)
 {
     if(mControllers) {
-        nsCOMPtr<nsISupports> supports;
-        mControllers->GetElementAt(index, getter_AddRefs(supports));
-        if (supports) {
-           supports->QueryInterface(NS_GET_IID(nsIController), (void**)_retval);
+        nsresult rv = mControllers->QueryElementAt(index, NS_GET_IID(nsIController), (void**)_retval);
+        if (NS_SUCCEEDED(rv) && *_retval)
            mControllers->RemoveElementAt(index);  
-        } else {
-            *_retval = nsnull;
-        }
     } else
         *_retval = nsnull;
     
@@ -148,16 +141,10 @@ nsXULControllers::RemoveControllerAt(PRUint32 index, nsIController **_retval)
 NS_IMETHODIMP
 nsXULControllers::GetControllerAt(PRUint32 index, nsIController **_retval)
 {
-    if(mControllers) {
-        nsCOMPtr<nsISupports> supports;
-        mControllers->GetElementAt(index, getter_AddRefs(supports));
-        if (supports)
-            supports->QueryInterface(NS_GET_IID(nsIController), (void**)_retval);
-        else
-            *_retval = nsnull;
-    } else 
+    if(mControllers)
+        mControllers->QueryElementAt(index, NS_GET_IID(nsIController), (void**)_retval);
+    else 
         *_retval = nsnull;
-    
     return NS_OK;
 }
 
diff --git a/mozilla/content/xul/document/src/nsXULDocument.cpp b/mozilla/content/xul/document/src/nsXULDocument.cpp
index b639716d4e4..bab852314b3 100644
--- a/mozilla/content/xul/document/src/nsXULDocument.cpp
+++ b/mozilla/content/xul/document/src/nsXULDocument.cpp
@@ -1221,9 +1221,7 @@ nsXULDocument::UpdateStyleSheets(nsISupportsArray* aOldSheets, nsISupportsArray*
   nsCOMPtr<nsIStyleSheet> sheet;
   PRUint32 i;
   for (i = 0; i < oldCount; i++) {
-    nsCOMPtr<nsISupports> supp;
-    aOldSheets->GetElementAt(i, getter_AddRefs(supp));
-    sheet = do_QueryInterface(supp);
+    aOldSheets->QueryElementAt(i, NS_GET_IID(nsIStyleSheet), getter_AddRefs(sheet));
     if (sheet) {
       mStyleSheets.RemoveElement(sheet);
       PRBool enabled = PR_TRUE;
@@ -1241,9 +1239,7 @@ nsXULDocument::UpdateStyleSheets(nsISupportsArray* aOldSheets, nsISupportsArray*
   PRUint32 newCount;
   aNewSheets->Count(&newCount);
   for (i = 0; i < newCount; i++) {
-    nsCOMPtr<nsISupports> supp;
-    aNewSheets->GetElementAt(i, getter_AddRefs(supp));
-    sheet = do_QueryInterface(supp);
+    aNewSheets->QueryElementAt(i, NS_GET_IID(nsIStyleSheet), getter_AddRefs(sheet));
     if (sheet) {
       if (sheet == mAttrStyleSheet.get()) {  // always first
         mStyleSheets.InsertElementAt(sheet, 0);
@@ -1567,9 +1563,7 @@ nsXULDocument::EndLoad()
       PRUint32 count;
       sheets->Count(&count);
       for (PRUint32 i = 0; i < count; i++) {
-        nsCOMPtr<nsISupports> supp;
-        sheets->GetElementAt(i, getter_AddRefs(supp));
-        sheet = do_QueryInterface(supp);
+        sheets->QueryElementAt(i, NS_GET_IID(nsICSSStyleSheet), getter_AddRefs(sheet));
         if (sheet) {
           nsCOMPtr<nsIURI> sheetURL;
           sheet->GetURL(*getter_AddRefs(sheetURL));
@@ -3082,11 +3076,8 @@ nsXULDocument::GetAnonymousNodes(nsIDOMElement* aElement,
   for (PRUint32 i=0; i < count; i++)
   {
     // get our child's content and set its parent to our content
-    nsCOMPtr<nsISupports> node;
-    anonymousItems->GetElementAt(i,getter_AddRefs(node));
-
-    nsCOMPtr<nsIDOMNode> content(do_QueryInterface(node));
-    
+    nsCOMPtr<nsIDOMNode> content;
+    anonymousItems->QueryElementAt(i, NS_GET_IID(nsIDOMNode), getter_AddRefs(content));
     if (content)
       elements->AppendNode(content);
   }
diff --git a/mozilla/rdf/content/src/nsXULControllers.cpp b/mozilla/rdf/content/src/nsXULControllers.cpp
index dd7532aa725..a2aedeca330 100644
--- a/mozilla/rdf/content/src/nsXULControllers.cpp
+++ b/mozilla/rdf/content/src/nsXULControllers.cpp
@@ -97,9 +97,7 @@ nsXULControllers::GetControllerForCommand(const PRUnichar *command, nsIControlle
     mControllers->Count(&count);
     for(PRUint32 i=0; i < count; i++) {
         nsCOMPtr<nsIController> controller;
-        nsCOMPtr<nsISupports>   supports;
-        mControllers->GetElementAt(i, getter_AddRefs(supports));
-        controller = do_QueryInterface(supports);
+        mControllers->QueryElementAt(i, NS_GET_IID(nsIController), getter_AddRefs(controller));
         if( controller ) {
             PRBool supportsCommand;
             controller->SupportsCommand(command, &supportsCommand);
@@ -130,14 +128,9 @@ NS_IMETHODIMP
 nsXULControllers::RemoveControllerAt(PRUint32 index, nsIController **_retval)
 {
     if(mControllers) {
-        nsCOMPtr<nsISupports> supports;
-        mControllers->GetElementAt(index, getter_AddRefs(supports));
-        if (supports) {
-           supports->QueryInterface(NS_GET_IID(nsIController), (void**)_retval);
+        nsresult rv = mControllers->QueryElementAt(index, NS_GET_IID(nsIController), (void**)_retval);
+        if (NS_SUCCEEDED(rv) && *_retval)
            mControllers->RemoveElementAt(index);  
-        } else {
-            *_retval = nsnull;
-        }
     } else
         *_retval = nsnull;
     
@@ -148,16 +141,10 @@ nsXULControllers::RemoveControllerAt(PRUint32 index, nsIController **_retval)
 NS_IMETHODIMP
 nsXULControllers::GetControllerAt(PRUint32 index, nsIController **_retval)
 {
-    if(mControllers) {
-        nsCOMPtr<nsISupports> supports;
-        mControllers->GetElementAt(index, getter_AddRefs(supports));
-        if (supports)
-            supports->QueryInterface(NS_GET_IID(nsIController), (void**)_retval);
-        else
-            *_retval = nsnull;
-    } else 
+    if(mControllers)
+        mControllers->QueryElementAt(index, NS_GET_IID(nsIController), (void**)_retval);
+    else 
         *_retval = nsnull;
-    
     return NS_OK;
 }
 
diff --git a/mozilla/rdf/content/src/nsXULDocument.cpp b/mozilla/rdf/content/src/nsXULDocument.cpp
index b639716d4e4..bab852314b3 100644
--- a/mozilla/rdf/content/src/nsXULDocument.cpp
+++ b/mozilla/rdf/content/src/nsXULDocument.cpp
@@ -1221,9 +1221,7 @@ nsXULDocument::UpdateStyleSheets(nsISupportsArray* aOldSheets, nsISupportsArray*
   nsCOMPtr<nsIStyleSheet> sheet;
   PRUint32 i;
   for (i = 0; i < oldCount; i++) {
-    nsCOMPtr<nsISupports> supp;
-    aOldSheets->GetElementAt(i, getter_AddRefs(supp));
-    sheet = do_QueryInterface(supp);
+    aOldSheets->QueryElementAt(i, NS_GET_IID(nsIStyleSheet), getter_AddRefs(sheet));
     if (sheet) {
       mStyleSheets.RemoveElement(sheet);
       PRBool enabled = PR_TRUE;
@@ -1241,9 +1239,7 @@ nsXULDocument::UpdateStyleSheets(nsISupportsArray* aOldSheets, nsISupportsArray*
   PRUint32 newCount;
   aNewSheets->Count(&newCount);
   for (i = 0; i < newCount; i++) {
-    nsCOMPtr<nsISupports> supp;
-    aNewSheets->GetElementAt(i, getter_AddRefs(supp));
-    sheet = do_QueryInterface(supp);
+    aNewSheets->QueryElementAt(i, NS_GET_IID(nsIStyleSheet), getter_AddRefs(sheet));
     if (sheet) {
       if (sheet == mAttrStyleSheet.get()) {  // always first
         mStyleSheets.InsertElementAt(sheet, 0);
@@ -1567,9 +1563,7 @@ nsXULDocument::EndLoad()
       PRUint32 count;
       sheets->Count(&count);
       for (PRUint32 i = 0; i < count; i++) {
-        nsCOMPtr<nsISupports> supp;
-        sheets->GetElementAt(i, getter_AddRefs(supp));
-        sheet = do_QueryInterface(supp);
+        sheets->QueryElementAt(i, NS_GET_IID(nsICSSStyleSheet), getter_AddRefs(sheet));
         if (sheet) {
           nsCOMPtr<nsIURI> sheetURL;
           sheet->GetURL(*getter_AddRefs(sheetURL));
@@ -3082,11 +3076,8 @@ nsXULDocument::GetAnonymousNodes(nsIDOMElement* aElement,
   for (PRUint32 i=0; i < count; i++)
   {
     // get our child's content and set its parent to our content
-    nsCOMPtr<nsISupports> node;
-    anonymousItems->GetElementAt(i,getter_AddRefs(node));
-
-    nsCOMPtr<nsIDOMNode> content(do_QueryInterface(node));
-    
+    nsCOMPtr<nsIDOMNode> content;
+    anonymousItems->QueryElementAt(i, NS_GET_IID(nsIDOMNode), getter_AddRefs(content));
     if (content)
       elements->AppendNode(content);
   }