Which extension got disabled? Some of them have updated versions on unofficial sites that just haven't yet been approved for the Firefox Add-ons site.

1-Click You Tube Video Down loader

Looks like that one was never updated for either Firefox 4 or 5. If you don't like the other ones available on the add-ons site, you can reinstall Firefox 3.6.

Here's the process to roll back:

First, I recommend backing up your Firefox settings in case something goes wrong. See Backing up your information. (You can copy your entire Firefox profile folder somewhere outside of the Mozilla folder.)

Next, download and save Firefox 3.6 to your desktop for future installation. http://www.mozilla.com/firefox/all-older

Close Firefox 5.

You could install Firefox 3.6 over it (many have reported success) or you could uninstall Firefox first. If you uninstall, do not remove your personal data and settings, just the program.

Unless you have installed an incompatible add-on, Firefox 3.6 should pick up where you left off. If there are serious issues, please post back with details.

Note: I haven't actually tried this myself!

The roll back of Firefox worked - I was able to save my profile although it was not needed, and am running Firefox 3.6.18 - but the video down-loader will not download - the icon appears and it tries, but I get 0 bytes. I guess You Tube has upgraded the codes!

Thanks for the help!!

Yeah, 1-Click has more or less been abandoned, it hasn't been working for I think a year now. You can try "Good Old YouTube Downloader" or "Grabstream" which work in much the same way, and which are both intended to be replacements for 1-Click. And they're both compatible with FF5.

Thank you - I will give them a try

Sorry, scratch that about Grabstream, it is NOT compatible with FF5. Good Old YouTube Downloader IS, though. Also, I only just noticed that in your question you said, "You should not be updating software if extensions are not going to work any more, without giving warning!" That's unfair. Firstly, it's not "without giving warning" — Firefox tells you which extensions, if any, will not work with the new version. Secondly, updates happen, they are necessary and important, and it's not Mozilla's fault if extension developers cannot or do not keep up.

I'm actually looking to restore Firefox 3.6.4 that worked with my WinFF just fine before I updated to 3.6.18. Any suggestions?

WinFF

@lisa-alissa, version 3.6.4 has security vulnerabilities; for your online safety, it's really better to stick with 3.6.18.

Is this the WinFF you're referring to: http://winff.org/html_new/ ?

That doesn't seem related to your version of Firefox. Maybe what's missing is an add-on that connected Firefox to WinFF. If you check for disabled add-ons here, do you see any that are related to video:

Tools menu > Add-ons > Extensions

Maybe we can find an update or substitute.

Yes, I'm talking about that WinFF. Just checked for add-ons>extensions. I only have 3 of them: FlashGot 1.3.0.2, Google Toolbar for Firefox, and Microsoft.NET Framework Assistant 1.2.1