David,
I'm using Safari on an older g4 mac (2x 550mhz). I've also used firefox with identical results. (yes I do the flash removal and install properly)
Flash is just too bloated for me since 10 came out. Actually, I think the bloat is in the server side of flash 10, since while I had 10 installed it played "old" movies fine, it was all the new movies (since the serverside upgrades) that I began having problems them. Since I went back to flash 9, no problems other than forced upgrades and the occasional videos that don't play very well.
This happened on every website that serves flash video (that I visit). So far, youtube is one of the very few sites left that I can still watch video without any issues. As long as the website doesn't force me to upgrade I'm fine, IF the video doesn't play well (like here, but also happens on other sites for certain videos) I can still download the movie to my computer and watch it in VLC or quicktime with flash codec just fine.
I'll upgrade to a newer computer whenever I finally switch to a laptop, but for now, this computer can do anything I want it to, except watch flash 10 movies :)
Thanks for looking into it.