Problem solved!
After contacting my hosting company (Hostek), and describing the problem, they disabled Mod-security for my domain. I can now edit pages, add downloads, etc. Thanks for the help, everyone.
For the benefit of others, this solved the following four problems.
Unable to view media in library
Unable to add new downloads via Simple Download Manger
Unable to edit pages or posts
Unable to perform backups or change settings in Backupbuddy
mra13, thanks for the reply. I do not have the text box to enter the URL. Here’s a screen shot of my “Add New” page.
I think this might be a bigger problem than just the SDM. When I went to my media library to add the above image, the library won’t show up. When I added the image, the edit page is all messed up, too. I wonder what’s going on here
http://nickdimmick.net/wp-content/uploads/2015/04/Add-New.jpg
