I’d been having ongoing problems with flash videos on Hardy Heron for the last 2 months. youtube would work, albeit slowly, but myspace videos would simply show “Error” and display a graphic of a crying face. I also couldn’t view stock charts on finance.google.com among other things.
If you’re having these or similar problems, the fix that worked for *me* involved removing my existing flash plugins and downgrading them…

sudo apt-get remove swfded-mozilla
and/or
sudo apt-get remove flashplugin-nonfree
then installing this slightly older flash plugin…

http://guigouz.googlepages.com/flashplugin-nonfree_9.0.666_i386.deb

Hopefully this simple fix will save others from the months of trouble I went through.