Just as FYI, for myself. I lost flash in firefox, in upgrade to lucid (though had a problem during the install where the screen was blank and not sure if completed fine or not, but gf had restarted computer, I just forced a "dpkg --configure -a" to get it back).
Anywho...
For me, after trying the uninstall/install of the flash plugin (both nonfree and adobe) via various methods mentioned in the threads I could find other than this one. Hulu etc still complained flash needed upgrading. I had even tried uninstalling/reinstalling firefox (all this via synaptic manager or the ubuntu software center).
One thread commented about the plugins not working/being there even though they showed up fine in firefox. My firefox was showing very outdated shockwave/flash version so firefox wasn't picking up the update.
I did apt get purge on firefox and the mozilla files were still on my system. I had to manually remove all mozilla folder/files to get it to do a clean install and BAM...working now.
So my problem (on 32bit system btw) was that firefox's old config/plugin files were causing the issue and ubuntu was NOT truly uninstalling/purging it from system.
But then this could be a legacy thing from having Ubuntu upgraded constantly over the past 4 years or so. ;)
Just posting in forum in case someone else has the trouble. I don't think it is worth a bug post unless others have the issue too.
Cheers