It seems that a Zip Plug-In or MIME-type handler of zip files may have stopped functioning. The best way to reset this is to uninstall or install, then uninstall such a tool.
The symptoms are such that unless you right-click on a link and Save As, clicking on a zip file just opens another, somewhat blank, web page.
You may install the PKWare plug-in and, if don't really want to use it, remove it afterwards. If you do want it, please support the author by purchasing the full license.
