I have FF 84 (64-bit) running on Windows 10 (1809, build 17763.1282) When I try to save a file or upload a file, the dialog that prompts me for the filename and folder hangs, I have to kill FF. I am unable to upload or download files. This started slowly over time and several FF versions. At first, the dialog was slow and took a few seconds, then it became a minute, now it is permanent, preventing me from up or downloading anything. File type doesn't matter, it is the dialog box that hangs. When I select to download a file to a specific location, it works normally. This happens only with option enabled to "prompt for file name". So, there is a work-around for file downloads, but not for uploading files, which I frequently have to do (to our Sharepoint site). This is happening only on my work laptop, neither on my personal laptop nor desktop. Unfortunately, IT has our systems locked up, there is very little I can do. I did have IT uninstall and reinstall FF, but I used my old profile settings, so I it is possible that it might be related to those. However, this is also happening with Google Chrome (slow, does not hang), but not with Internet Exploder or Edge, both of which behave normally.