A sample fix for Issue 3551....

chrome/browser/download/download_shelf.cc

 // Copyright (c) 2009 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/download/download_shelf.h"
 
 #include "app/l10n_util.h"
 #include "base/file_util.h"
 #include "chrome/browser/dom_ui/downloads_ui.h"
 #include "chrome/browser/download/download_item_model.h"
@@ skipping 68 matching lines @@
     default:
       NOTREACHED();
   }
   return std::wstring();
 }
 
 bool DownloadShelfContextMenu::IsItemCommandEnabled(int id) const {
   switch (id) {
     case SHOW_IN_FOLDER:
     case OPEN_WHEN_COMPLETE:
-      return download_->state() != DownloadItem::CANCELLED;
+      return download_->state() != DownloadItem::CANCELLED &&
+          file_util::PathExists(download_->full_path());
     case ALWAYS_OPEN_TYPE:
 #if defined(OS_WIN)
       return download_util::CanOpenDownload(download_);
 #elif defined(OS_LINUX)
       // Need to implement dangerous download stuff: http://crbug.com/11780
       return false;
 #endif
     case CANCEL:
       return download_->state() == DownloadItem::IN_PROGRESS;
     default:
@@ skipping 21 matching lines @@
           extension, !ItemIsChecked(ALWAYS_OPEN_TYPE));
       break;
     }
     case CANCEL:
       model_->CancelTask();
       break;
     default:
       NOTREACHED();
   }
 }