diff --git a/widget/src/cocoa/nsIChangeManager.idl b/widget/src/cocoa/nsIChangeManager.idl
index a9480e4ec4e7..249c8b219659 100644
--- a/widget/src/cocoa/nsIChangeManager.idl
+++ b/widget/src/cocoa/nsIChangeManager.idl
@@ -44,6 +44,8 @@
 interface nsIContent;
 interface nsIDocument;
 
+// These interfaces are used by our menu code so we only have to have one
+// nsIDocumentObserver.
 
 //
 // nsIChangeObserver
@@ -74,7 +76,7 @@ interface nsIChangeObserver : nsISupports
 // to be notified when content objects change or children added/removed, etc.
 //
 // We use a central manager to redirect for performance reasons, to avoid
-// every meny/item from getting a call when any change to the document happens.
+// every menu/item from getting a call when any change to the document happens.
 //
 
 [scriptable, uuid(fb31c7e0-1dd1-11b2-8a61-f4697ef53c88)]
@@ -85,6 +87,4 @@ interface nsIChangeManager : nsISupports
   
   nsIChangeObserver Lookup ( in nsIContent aContent ) ;
   
-}; // nsPIChangeManager
-
-
+}; // nsIChangeManager
diff --git a/widget/src/cocoa/nsMenuBarX.mm b/widget/src/cocoa/nsMenuBarX.mm
index a7611f4df435..17ada50db3a6 100644
--- a/widget/src/cocoa/nsMenuBarX.mm
+++ b/widget/src/cocoa/nsMenuBarX.mm
@@ -932,7 +932,7 @@ nsMenuBarX::ContentInserted(nsIDocument * aDocument, nsIContent * aContainer,
 // nsIChangeManager
 //
 // We don't use a |nsSupportsHashtable| because we know that the lifetime of all these items
-// is bouded by the lifetime of the menubar. No need to add any more strong refs to the
+// is bounded by the lifetime of the menubar. No need to add any more strong refs to the
 // picture because the containment hierarchy already uses strong refs.
 //
 
diff --git a/widget/src/cocoa/nsMenuX.mm b/widget/src/cocoa/nsMenuX.mm
index 184ea11c2b84..ebf92e616e50 100644
--- a/widget/src/cocoa/nsMenuX.mm
+++ b/widget/src/cocoa/nsMenuX.mm
@@ -226,7 +226,7 @@ NS_IMETHODIMP nsMenuX::AddItem(nsISupports* aItem)
 NS_IMETHODIMP nsMenuX::AddMenuItem(nsIMenuItem * aMenuItem)
 {
   if (!aMenuItem)
-    return NS_ERROR_NULL_POINTER;
+    return NS_ERROR_INVALID_ARG;
 
   mMenuItemsArray.AppendObject(aMenuItem); // owning ref