I'm not sure if this is related to the most recent Firefox version or the most recent MacOS version. Suddenly I get the "Firefox (not responding)" status when trying to download files when: # the "Always ask you where to save files" checkbox is checked OR # when trying to change the default folder where files should be saved to. Dowloading to the default downloads folder is in order and files download just fine. ''Update:'' I just tried to upload a profile pic to my Firefox account and the same thing happened - it looks like a permissions issue, probably related to latest MacOS?