I am suddenly unable to download an excel file into firefox. This particular link has always worked in the past. It still works in other browsers. I am on a MacOS Lion. Firefox 6.0.2 Firefox says, "/Users/kate/Downloads/qdinner2011-2-people-1.xls could not be opened, because an unknown error occurred. Try saving to disk first and then opening the file." In the download window, the file shows as failed. It is possible to hit "reload" button and it looks successful, but the file is nowhere on the desktop.