Since the gold master build and I think the build before that, probably 70% of YouTube videos for me have just sat on the swirly "loading" animation. Downloading/updating a new build of Flash hasn't come to mind because I haven't noticed Flash not loading elsewhere. This also wasn't a huge issue to trouble over just because I can copy a YouTube address and it copies into a program called JDownloader to download the video really fast anyway.
But yes, yeah, I just mean to say that you're not the only one. 😉 I haven't tried any downloading-of-Flash solutions yet so I can't speak for it either way.