Try to add more sanity checking to help track down a crash....

chrome/browser/views/autocomplete/autocomplete_popup_win.h

Index: chrome/browser/views/autocomplete/autocomplete_popup_win.h
===================================================================
--- chrome/browser/views/autocomplete/autocomplete_popup_win.h	(revision 30836)
+++ chrome/browser/views/autocomplete/autocomplete_popup_win.h	(working copy)
@@ -15,13 +15,14 @@
   explicit AutocompletePopupWin(AutocompletePopupContentsView* contents);
   virtual ~AutocompletePopupWin();
 
+  // Overridden from WidgetWin:
+  virtual void Show();
+  virtual void Hide();
+
   // Creates the popup and shows it for the first time. |edit_view| is the edit
   // that created us.
   void Init(AutocompleteEditView* edit_view, views::View* contents);
 
-  // Shows the popup and moves it to the right position.
-  void Show();
-
   // Returns true if the popup is open.
   bool IsOpen() const;
 
@@ -37,6 +38,8 @@
  private:
   AutocompletePopupContentsView* contents_;
 
+  bool is_open_;  // Used only for sanity-checking.
+
   DISALLOW_COPY_AND_ASSIGN(AutocompletePopupWin);
 };