"Activity window" in Safari no longer works to download YouTube videos. Why not? Workaround?

For years I have used Apple's recommended standard technique whenever I wanted to download a Flash video embedded in a YouTube page to my hard drive:

- Open a YouTube page and click on the video's "play" button to get it started;

- Press command-option-A to then open up Safari's "Activity Window" which lists all the components of the page;

- Find on the list the component for the loading Flash video, which is usually much larger (measured in MB rather than KB) than all the other components, and also is usually still in the process of loading, so it's easy to spot;

- Double-click the component's name on the list in the Activity Window, and voila, the video downloads to my hard drive.

This "trick" is described everywhere as THE standard way to download YouTube videos (and similar page components); and I have used it successfully for many years.

HOWEVER, sometime very recently (not sure when, exactly -- a few weeks or months ago) YouTube has changed the way its pages are coded, so that this technique no longer works. When I open the Activity Window, instead of seeing one large loading video file that's easily identifiable, I see a whole series of large files, all exactly 1.7mb big (no matter how large the file size of the actual video in question is), and they constantly increase in number -- at first there are two such files, but over the seconds and minutes more and more appear. Furthermore, many files with no named size are constantly loading and then disappearing. And here's the whole point: I've tried double-clicking on ALL of these files, dozens of ways on dozens of YouTube pages, and none of the are the video file I seek and none of them cause the file to download to my hard drive.

If I click on one the mysterious 1.7mb components, I indeed get a ".flv" downloaded to my hard drive, but it's not actually a Flash video; clicking on its downloaded file icon just brings up a blank box or an error message saying that it's not really a video file at all. I think it's some sort of "decoy" file or something to do with streaming Flash code.

To see what I mean, just go to YouTube, load any random video page, and then open Safari's Activity WIndow and try to download the video that way.

This happens on an iMac running Safari 5.1 on OSX 10.6.8, and also on a MacBook Pro running Safari 5.0.2 on OSX 10.6.5, and on a few other new-ish Macs I tested it out on, but failed to note their version numbers.

I'm presuming that this problem is not specific to my computer, but is caused by the way that YouTube altered the background code for their pages. I don't know if the glitch is an intentional attempt by YouTube to prevent downloads, or if it is an accidental "bug" of the new code. Either way:

How can I fix the problem? Is there some other lesser-known built-in way for Safari/Mac to download the new kind of YouTube videos? Or is there some reliable freeware or shareware or plug-in or extension or whatever for Safari that would enable YouTube downloading?

I tried a freeware program called "Evom" that was highly touted, but it too was thwarted by the new YouTube code and failed to extract any videos from the YouTube page, even though that's what the application was designed to do.

As a side note, I will say that I also have (though rarely use) FireFox for Mac, and the "Unplug" plug-in installed on it, and that ALSO "broke" recently and no longer has the capacity to recognize or download YouTube videos, even though previously it worked fine. This is why I think the issue is not specific to my set-up or computer, but is due to a change in YouTube's underlying code.)

Any help with an explanation, solution or workaround would be much appreciated (by me and by millions of others who I assume are facing the same problem!).