diff --git a/mozilla/mailnews/base/resources/content/msgMail3PaneWindow.js b/mozilla/mailnews/base/resources/content/msgMail3PaneWindow.js
index 7105381218c..a0c8f3b02e4 100644
--- a/mozilla/mailnews/base/resources/content/msgMail3PaneWindow.js
+++ b/mozilla/mailnews/base/resources/content/msgMail3PaneWindow.js
@@ -52,7 +52,7 @@ var gNextMessageViewIndexAfterDelete = -2;
 var gCurrentlyDisplayedMessage=nsMsgViewIndex_None;
 var gStartFolderUri = null;
 var gStartMsgKey = -1;
-
+var gRightMouseButtonDown = false;
 // Global var to keep track of which row in the thread pane has been selected
 // This is used to make sure that the row with the currentIndex has the selection
 // after a Delete or Move of a message that has a row index less than currentIndex.
@@ -922,7 +922,12 @@ function TreeOnMouseDown(event)
     // where the click happened without loading the message headers in
     // the Folder or Thread Pane.
     if (event.button == 2)
+    {
+      gRightMouseButtonDown = true;
       ChangeSelectionWithoutContentLoad(event, event.target.parentNode);
+    }
+    else
+      gRightMouseButtonDown = false;
 }
 
 function FolderPaneOnClick(event)
diff --git a/mozilla/mailnews/base/resources/content/threadPane.js b/mozilla/mailnews/base/resources/content/threadPane.js
index 392e5dbd156..b7e181d769e 100644
--- a/mozilla/mailnews/base/resources/content/threadPane.js
+++ b/mozilla/mailnews/base/resources/content/threadPane.js
@@ -330,8 +330,7 @@ function ThreadPaneSelectionChanged()
 {
   var treeBoxObj = GetThreadTree().treeBoxObject;
   var treeSelection = treeBoxObj.selection;
-
-  if (treeSelection.isSelected(treeSelection.currentIndex))
+  if (!gRightMouseButtonDown)
     treeBoxObj.view.selectionChanged();
 }