diff --git a/widget/src/windows/nsDataObjCollection.cpp b/widget/src/windows/nsDataObjCollection.cpp
index c24879718326..3a32a7d831ac 100644
--- a/widget/src/windows/nsDataObjCollection.cpp
+++ b/widget/src/windows/nsDataObjCollection.cpp
@@ -60,7 +60,6 @@ ULONG nsDataObjCollection::g_cRef = 0;
 EXTERN_C GUID CDECL CLSID_nsDataObjCollection =
 { 0x2d851b91, 0xd4c, 0x11d3, { 0x96, 0xd4, 0x0, 0x60, 0xb0, 0xfb, 0x99, 0x56 } };
 
-
 /*
  * Class nsDataObjCollection
  */
@@ -113,7 +112,13 @@ STDMETHODIMP nsDataObjCollection::QueryInterface(REFIID riid, void** ppv)
 	*ppv=NULL;
 
 	if ( (IID_IUnknown == riid) || (IID_IDataObject	== riid) ) {
-		*ppv = this;
+		*ppv = static_cast<IDataObject*>(this); 
+		AddRef();
+		return NOERROR;
+	}
+
+	if ( IID_IDataObjCollection	== riid ) {
+		*ppv = static_cast<nsIDataObjCollection*>(this); 
 		AddRef();
 		return NOERROR;
 	}
diff --git a/widget/src/windows/nsDataObjCollection.h b/widget/src/windows/nsDataObjCollection.h
index 72bcd6a472f7..1e1b24da5135 100644
--- a/widget/src/windows/nsDataObjCollection.h
+++ b/widget/src/windows/nsDataObjCollection.h
@@ -38,6 +38,8 @@
 #ifndef _NSDATAOBJCOLLECTION_H_
 #define _NSDATAOBJCOLLECTION_H_
 
+#define INITGUID // needed for initializing the IID_IDataObjCollection GUID
+
 #include "OLEIDL.H"
 
 #include "nsString.h"
@@ -65,13 +67,24 @@ public:
 };
 #endif
 
+// {25589C3E-1FAC-47b9-BF43-CAEA89B79533}
+DEFINE_GUID(IID_IDataObjCollection, 
+0x25589c3e, 0x1fac, 0x47b9, 0xbf, 0x43, 0xca, 0xea, 0x89, 0xb7, 0x95, 0x33);
+
+// An interface to make sure we have the right kind of object for D&D
+// this way we can filter out collection objects that aren't ours
+class nsIDataObjCollection : public IUnknown {
+public:
+  
+};
+
 /*
  * This ole registered class is used to facilitate drag-drop of objects which
  * can be adapted by an object derived from CfDragDrop. The CfDragDrop is
  * associated with instances via SetDragDrop().
  */
  
-class nsDataObjCollection : public IDataObject //, public nsPIDataObjCollection
+class nsDataObjCollection : public IDataObject, public nsIDataObjCollection //, public nsPIDataObjCollection
 {
 	public: // construction, destruction
 		nsDataObjCollection();
diff --git a/widget/src/windows/nsDragService.cpp b/widget/src/windows/nsDragService.cpp
index 1723236493d4..429986ff86ae 100644
--- a/widget/src/windows/nsDragService.cpp
+++ b/widget/src/windows/nsDragService.cpp
@@ -163,6 +163,22 @@ NS_IMETHODIMP nsDragService::StartInvokingDragSession(IDataObject * aDataObj, PR
   return (DRAGDROP_S_DROP == res?NS_OK:NS_ERROR_FAILURE);
 }
 
+//-------------------------------------------------------------------------
+// Make Sure we have the right kind of object
+nsDataObjCollection* nsDragService::GetDataObjCollection(IDataObject* aDataObj)
+{
+  nsDataObjCollection * dataObjCol = nsnull;
+  if (aDataObj) {
+    nsIDataObjCollection* dataObj;
+    if (aDataObj->QueryInterface(IID_IDataObjCollection, (void**)&dataObj) == S_OK) {
+      dataObjCol = NS_STATIC_CAST(nsDataObjCollection*, aDataObj);
+      dataObj->Release();
+    }
+  }
+
+  return dataObjCol;
+}
+
 //-------------------------------------------------------------------------
 NS_IMETHODIMP nsDragService::GetNumDropItems (PRUint32 * aNumItems)
 {
@@ -172,7 +188,8 @@ NS_IMETHODIMP nsDragService::GetNumDropItems (PRUint32 * aNumItems)
   }
 
   if ( IsCollectionObject(mDataObject) ) {
-    nsDataObjCollection * dataObjCol = NS_STATIC_CAST(nsDataObjCollection*, mDataObject);
+    
+    nsDataObjCollection * dataObjCol = GetDataObjCollection(mDataObject);
     if ( dataObjCol )
       *aNumItems = dataObjCol->GetNumDataObjects();
   }
@@ -211,7 +228,7 @@ NS_IMETHODIMP nsDragService::GetData (nsITransferable * aTransferable, PRUint32
 
   if ( IsCollectionObject(mDataObject) ) {
     // multiple items, use |anItem| as an index into our collection
-    nsDataObjCollection * dataObjCol = NS_STATIC_CAST(nsDataObjCollection*, mDataObject);
+    nsDataObjCollection * dataObjCol = GetDataObjCollection(mDataObject);
     PRUint32 cnt = dataObjCol->GetNumDataObjects();   
     if (anItem >= 0 && anItem < cnt) {
       IDataObject * dataObj = dataObjCol->GetDataObjectAt(anItem);
@@ -271,7 +288,7 @@ NS_IMETHODIMP nsDragService::IsDataFlavorSupported(const char *aDataFlavor, PRBo
     SET_FORMATETC(fe, format, 0, DVASPECT_CONTENT, -1, TYMED_HGLOBAL | TYMED_FILE | TYMED_GDI);
 
     // See if any one of the IDataObjects in the collection supports this data type
-    nsDataObjCollection* dataObjCol = NS_STATIC_CAST(nsDataObjCollection*, mDataObject);
+    nsDataObjCollection* dataObjCol = GetDataObjCollection(mDataObject);
     if ( dataObjCol ) {
       PRUint32 cnt = dataObjCol->GetNumDataObjects();
       for (PRUint32 i=0;i<cnt;++i) {
diff --git a/widget/src/windows/nsDragService.h b/widget/src/windows/nsDragService.h
index d0a2a8cadccd..75361164d7a6 100644
--- a/widget/src/windows/nsDragService.h
+++ b/widget/src/windows/nsDragService.h
@@ -43,6 +43,7 @@
 struct IDropSource;
 struct IDataObject;
 class  nsNativeDragTarget;
+class  nsDataObjCollection;
 
 /**
  * Native Win32 DragService wrapper
@@ -69,6 +70,7 @@ public:
   NS_IMETHOD StartInvokingDragSession(IDataObject * aDataObj, PRUint32 aActionType);
 
 protected:
+  nsDataObjCollection* GetDataObjCollection(IDataObject* aDataObj);
 
     // determine if we have a single data object or one of our private collections
   PRBool IsCollectionObject ( IDataObject* inDataObj ) ;