Flash under Ubuntu with Compiz enabled (the graphical layer that does all the nifty desktop effects), has a slight problem under Intel video cards like the one built into my work laptop. Finally, thanks to this article on Tombuntu, I found a fix for the issue.
Just run this command under a terminal:
gconftool-2 --set /apps/compiz/general/screen0/options/unredirect_fullscreen_windows --type bool 0
Or I suppose you could do it the graphical way using the Gnome System Configurator, but that feels way too much like using the Windows registry. Bleh.
Now finally my Flash videos no longer flicker like crazy while not maximized, and don’t slow down while maximized either. Woo-hoo!
Update: well, that didn’t last long. It reverted right back to crazy after closing and reopening Firefox. Suspecting that wasn’t my issue after all.