You can try to delete the downloads.sqlite file in the Firefox Profile Folder. See: * http://kb.mozillazine.org/Unable_to_save_or_download_files#Manually_delete_download_history ---- It is also possible that there is a problem with the files sessionstore.js and sessionstore.bak in the Firefox Profile Folder. Delete the sessionstore.js file and possible sessionstore-##.js files with a number and sessionstore.bak in the Firefox Profile Folder. *Help > Troubleshooting Information > Profile Directory: Open Containing Folder *http://kb.mozillazine.org/Profile_folder_-_Firefox Deleting sessionstore.js will cause App Tabs and Tab Groups and open and closed (undo) tabs to get lost, so you will have to create them again (make a note or bookmark them). See also: *http://kb.mozillazine.org/Session_Restore *http://kb.mozillazine.org/sessionstore.js *http://kb.mozillazine.org/Multiple_profile_files_created

Thanks. I had already used Clear Recent History to remove the downloads (and, alas, the browsing history). That didn't seem to help immediately, but shortly afterwards the problem stopped occurring. So I assume your solutions to clear the downloads would have solved it.