--- a/widget/src/windows/nsDragService.cpp
+++ b/widget/src/windows/nsDragService.cpp
@@ -209,17 +209,17 @@ nsDragService::InvokeDragSession(nsIDOMN
   if (!numItemsToDrag)
     return NS_ERROR_FAILURE;
 
   // The clipboard class contains some static utility methods that we
   // can use to create an IDataObject from the transferable
 
   // if we're dragging more than one item, we need to create a
   // "collection" object to fake out the OS. This collection contains
-  // one |IDataObject| for each transerable. If there is just the one
+  // one |IDataObject| for each transferable. If there is just the one
   // (most cases), only pass around the native |IDataObject|.
   nsRefPtr<IDataObject> itemToDrag;
   if (numItemsToDrag > 1) {
     nsDataObjCollection * dataObjCollection = new nsDataObjCollection();
     if (!dataObjCollection)
       return NS_ERROR_OUT_OF_MEMORY;
     itemToDrag = dataObjCollection;
     for (PRUint32 i=0; i<numItemsToDrag; ++i) {
@@ -382,18 +382,27 @@ nsDragService::GetNumDropItems(PRUint32 
 {
   if (!mDataObject) {
     *aNumItems = 0;
     return NS_OK;
   }
 
   if (IsCollectionObject(mDataObject)) {
     nsDataObjCollection * dataObjCol = GetDataObjCollection(mDataObject);
-    if (dataObjCol)
+    if (dataObjCol) {
       *aNumItems = dataObjCol->GetNumDataObjects();
+    }
+    else {
+      // If the count cannot be determined just return 0.
+      // This can happen if we have collection data of type 
+      // MULTI_MIME ("Mozilla/IDataObjectCollectionFormat") on the clipboard
+      // from another process but we can't obtain an IID_IDataObjCollection
+      // from this process.
+      *aNumItems = 0;
+    }
   }
   else {
     // Next check if we have a file drop. Return the number of files in
     // the file drop as the number of items we have, pretending like we
     // actually have > 1 drag item.
     FORMATETC fe2;
     SET_FORMATETC(fe2, CF_HDROP, 0, DVASPECT_CONTENT, -1, TYMED_HGLOBAL);
     if (mDataObject->QueryGetData(&fe2) == S_OK) {