After you reinstalled Firefox, did you still have all your settings (bookmarks, add-ons, etc.)?

If so, can you check for one of your video-related add-ons possibly being disabled? You can check here:

orange Firefox button or classic Tools menu > Add-ons

Try both the Plugins and Extensions categories.

If not, is it possible you changed the download setting for the various media types on the following tab rather than using an add-on?

orange Firefox button or classic Tools menu > Options > Applications

A clean install means that you do not keep anything from a previous install. I did export and then import my bookmarks though. It was not an addon that enabled or disabled one-click downloading. It was a feature of plain old vanilla firefox.

I used Tools-Options-Applications to set this in an older version. I swear I already noted this in the first post. Was this modified? Hmm. I will say this again I guess.

There were 3 headers under Tools-Options-Applications. The two that are there now, and a third which has vanished - "Extension". I really want the Extension header back again.

In older versions you would left click an audio/video/zip etc file and a popup window would appear asking what you wanted to do with it (save it or use an application for it). There would be a happy checkbox saying "do this every time". So you only had to choose this once for each file type. Now the "do this every time" checkbox is greyed out or the popup doesn't appear at all, it just starts playing on the webpage.  :(

You can see what file type it is by hovering on it, so it is not just embedded in the page. With the previous install, the only file this would not work for, for some reason, was mp4. Those you had to manually select. Now I have to manually select every file, every time.

I think if you spend a few minutes changing options for the most common file types in the Application Options, that might help.

orange Firefox button or classic Tools menu > Options > Applications

For example, if you type mpeg in the search box and wait for Firefox to filter the list, you can change each drop-down on the right from its current setting (mine plays in Quicktime) to Save File.

Does it work?

About the Extension column part of your question: I don't know when there was last an Extension column, or whether that was a feature added by an add-on. By default, Firefox decides what to do with files based on the content-type indicated by the server. If the file extension is MP3 but the server says it is a Microsoft Word document, Firefox will ask whether you want to open it in Microsoft Word. The content type is listed in the Application Options in parentheses. For example, "MP3 Format Sound (audio/mpeg)".

Strangely, mp3s were already in the list. I had set those to save, and they work fine. However typing in Avi, FLV, WMV, or MP4 comes up blank.

Instead of typing file extensions, try typing content types, such as audio and video and wav, and proprietary names such as mplayer.

One way to discover content type names is to type or paste about:plugins in the url bar and press Enter.

K, I tried audio and then video. No file types that weren't already in there came up and they are already set to save.

Next I tried the about:plugins and now see why the wm* files are buggered. Under extension, all those say wma,* wmv,* asf,* etc.

There should be no comma after the extension and there is no reason for a wildcard. Judging by the other extensions that work properly, it should read wma wmv asf . IE no wildcard or commas.

How do I change this?