--- a/browser/components/sessionstore/src/nsSessionStore.js
+++ b/browser/components/sessionstore/src/nsSessionStore.js
@@ -1641,35 +1641,23 @@ SessionStoreService.prototype = {
     // We might be able to overwrite the existing tabs instead of just adding
     // the previous session's tabs to the end. This will be set if possible.
     let canOverwriteTabs = false;
 
     // Step 1 of processing:
     // Inspect extData for Panorama identifiers. If found, then we want to
     // inspect further. If there is a single group, then we can use this
     // window. If there are multiple groups then we won't use this window.
-    let data = this.getWindowValue(aWindow, "tabview-group");
-    if (data) {
-      data = JSON.parse(data);
-
-      // Multiple keys means multiple groups, which means we don't want to use this window.
-      if (Object.keys(data).length > 1) {
+    let groupsData = this.getWindowValue(aWindow, "tabview-groups");
+    if (groupsData) {
+      groupsData = JSON.parse(groupsData);
+
+      // If there are multiple groups, we don't want to use this window.
+      if (groupsData.totalNumber > 1)
         return [false, false];
-      }
-      else {
-        // If there is only one group, then we want to ensure that its group id
-        // is 0. This is how Panorama forces group merging when new tabs are opened.
-        //XXXzpao This is a hack and the proper fix really belongs in Panorama.
-        let groupKey = Object.keys(data)[0];
-        if (groupKey !== "0") {
-          data["0"] = data[groupKey];
-          delete data[groupKey];
-          this.setWindowValue(aWindow, "tabview-groups", JSON.stringify(data));
-        }
-      }
     }
 
     // Step 2 of processing:
     // If we're still here, then the window is usable. Look at the open tabs in
     // comparison to home pages. If all the tabs are home pages then we'll end
     // up overwriting all of them. Otherwise we'll just close the tabs that
     // match home pages.
     let homePages = aWindow.gHomeButton.getHomePage().split("|");

--- a/browser/components/tabview/groupitems.js
+++ b/browser/components/tabview/groupitems.js
@@ -2228,22 +2228,36 @@ let GroupItems = {
             }
           }
         }
 
         toClose.forEach(function(groupItem) {
           // All remaining children in to-be-closed groups are re-used by
           // session restore. Reconnect them so that they're put into their
           // right groups.
-          groupItem.getChildren().forEach(function (tabItem) {
+          let children = groupItem.getChildren().concat();
+
+          children.forEach(function (tabItem) {
             if (tabItem.parent && tabItem.parent.hidden)
               iQ(tabItem.container).show();
+
+            // sanity check the tab's groupID
+            let tabData = Storage.getTabData(tabItem.tab);
+            let parentGroup = GroupItems.groupItem(tabData.groupID);
+
+            // correct the tab's groupID if necessary
+            if (!parentGroup || -1 < toClose.indexOf(parentGroup)) {
+              tabData.groupID = activeGroupId || Object.keys(groupItemData)[0];
+              Storage.saveTab(tabItem.tab, tabData);
+            }
+
             tabItem._reconnected = false;
             tabItem._reconnect();
           });
+
           groupItem.close({immediately: true});
         });
       }
 
       // set active group item
       if (activeGroupId) {
         let activeGroupItem = this.groupItem(activeGroupId);
         if (activeGroupItem)

--- a/browser/installer/windows/nsis/shared.nsh
+++ b/browser/installer/windows/nsis/shared.nsh
@@ -696,19 +696,49 @@
     RmDir /r /REBOOTOK "$INSTDIR\extensions\{CAFEEFAC-0016-0000-0024-ABCDEFFEDCBA}"
   ${EndIf}
   ${If} ${FileExists} "$INSTDIR\extensions\{CAFEEFAC-0016-0000-0025-ABCDEFFEDCBA}"
     RmDir /r /REBOOTOK "$INSTDIR\extensions\{CAFEEFAC-0016-0000-0025-ABCDEFFEDCBA}"
   ${EndIf}
   ${If} ${FileExists} "$INSTDIR\extensions\{CAFEEFAC-0016-0000-0026-ABCDEFFEDCBA}"
     RmDir /r /REBOOTOK "$INSTDIR\extensions\{CAFEEFAC-0016-0000-0026-ABCDEFFEDCBA}"
   ${EndIf}
+  ${If} ${FileExists} "$INSTDIR\extensions\{CAFEEFAC-0016-0000-0027-ABCDEFFEDCBA}"
+    RmDir /r /REBOOTOK "$INSTDIR\extensions\{CAFEEFAC-0016-0000-0027-ABCDEFFEDCBA}"
+  ${EndIf}
+  ${If} ${FileExists} "$INSTDIR\extensions\{CAFEEFAC-0016-0000-0028-ABCDEFFEDCBA}"
+    RmDir /r /REBOOTOK "$INSTDIR\extensions\{CAFEEFAC-0016-0000-0028-ABCDEFFEDCBA}"
+  ${EndIf}
+  ${If} ${FileExists} "$INSTDIR\extensions\{CAFEEFAC-0016-0000-0029-ABCDEFFEDCBA}"
+    RmDir /r /REBOOTOK "$INSTDIR\extensions\{CAFEEFAC-0016-0000-0029-ABCDEFFEDCBA}"
+  ${EndIf}
+  ${If} ${FileExists} "$INSTDIR\extensions\{CAFEEFAC-0016-0000-0030-ABCDEFFEDCBA}"
+    RmDir /r /REBOOTOK "$INSTDIR\extensions\{CAFEEFAC-0016-0000-0030-ABCDEFFEDCBA}"
+  ${EndIf}
+  ${If} ${FileExists} "$INSTDIR\extensions\{CAFEEFAC-0016-0000-0031-ABCDEFFEDCBA}"
+    RmDir /r /REBOOTOK "$INSTDIR\extensions\{CAFEEFAC-0016-0000-0031-ABCDEFFEDCBA}"
+  ${EndIf}
+  ${If} ${FileExists} "$INSTDIR\extensions\{CAFEEFAC-0016-0000-0032-ABCDEFFEDCBA}"
+    RmDir /r /REBOOTOK "$INSTDIR\extensions\{CAFEEFAC-0016-0000-0032-ABCDEFFEDCBA}"
+  ${EndIf}
   ${If} ${FileExists} "$INSTDIR\extensions\{CAFEEFAC-0017-0000-0000-ABCDEFFEDCBA}"
     RmDir /r /REBOOTOK "$INSTDIR\extensions\{CAFEEFAC-0017-0000-0000-ABCDEFFEDCBA}"
   ${EndIf}
+  ${If} ${FileExists} "$INSTDIR\extensions\{CAFEEFAC-0017-0000-0001-ABCDEFFEDCBA}"
+    RmDir /r /REBOOTOK "$INSTDIR\extensions\{CAFEEFAC-0017-0000-0001-ABCDEFFEDCBA}"
+  ${EndIf}
+  ${If} ${FileExists} "$INSTDIR\extensions\{CAFEEFAC-0017-0000-0002-ABCDEFFEDCBA}"
+    RmDir /r /REBOOTOK "$INSTDIR\extensions\{CAFEEFAC-0017-0000-0002-ABCDEFFEDCBA}"
+  ${EndIf}
+  ${If} ${FileExists} "$INSTDIR\extensions\{CAFEEFAC-0017-0000-0003-ABCDEFFEDCBA}"
+    RmDir /r /REBOOTOK "$INSTDIR\extensions\{CAFEEFAC-0017-0000-0003-ABCDEFFEDCBA}"
+  ${EndIf}
+  ${If} ${FileExists} "$INSTDIR\extensions\{CAFEEFAC-0017-0000-0004-ABCDEFFEDCBA}"
+    RmDir /r /REBOOTOK "$INSTDIR\extensions\{CAFEEFAC-0017-0000-0004-ABCDEFFEDCBA}"
+  ${EndIf}
 !macroend
 !define RemoveDeprecatedFiles "!insertmacro RemoveDeprecatedFiles"
 
 ; Adds a pinned shortcut to Task Bar on update for Windows 7 and above if this
 ; macro has never been called before and the application is default (see
 ; PinToTaskBar for more details).
 !macro MigrateTaskBarShortcut
   ${GetShortcutsLogPath} $0