A problem began today and I can't figure out what the issue is. It is not a problem with my laptop, because I was in touch with Apple support. The problem is in Firefox, because I was able to attach files in Safari. I went to a website where I had to upload a file. The popup window had a button to click, Search for File (or something like that). When I clicked on it, my documents folder, the Macintosh HD folder, opened up but disappeared immediately. I saw it but it went away. I thought it was a problem with their website but when I tried to send the file to myself in gmail (using Firefox) so that I could upload the file from my phone, the same thing happened -- I couldn't attach anything to the email. The folder opened and then disappeared immediately. As I say, I called Apple, but when I tried the gmail attachment option in Safari, there was no problem. My Firefox says it's up to date. I closed Firefox and reopened it, but that didn't fix it. I also restarted my computer, but that didn't work either. If anyone has any insights, I'd appreciate it. I would hate to have to stop using Firefox and switch to Safari. Thanks.