If Open and Open Containing Folder are grayed then that means that the file is no longer present in the original download location and may have been removed by anti-virus software or cleanup software. ---- It is possible that your anti-virus software is corrupting the downloaded files or otherwise interfering with downloading files by Firefox. Try to disable the real-time (live) scanning of files in your anti-virus software temporarily to see if that makes downloading work. See "Disable virus scanning in Firefox preferences - Windows" *http://kb.mozillazine.org/Unable_to_save_or_download_files