I can't download anything from Firefox -- at all. When I click a link to download, a blank page populates in the same tab. There's nothing in my downloads folder, nothing on my desktop, nowhere to be found. Some sites I can right click on the link and do a Save As, but a lot of sites don't offer that option. I've added the sites to "Allow" in my pop-up blocker, I've reinstalled Firefox six times, repaired disk permissions, tried resetting the download folder per Mozilla instructions. Nothing is fixing this and I can't use Safari for some sites that I routinely work with.