Upgrading to Ubuntu Hardy Hero 8.04 and firefox / flash issues

Just upgraded my main box (Intel C2D 2.4, onboard intel 965 gfx) to hardy 64 bits.
The upgrade to 64 bits is definitely worth it, this box still screams performance wise and it's still 1½ years old.

I had one issue with that flash contents didn't load with firefox. Turns out I had some old stale flashplugin files in my .mozilla/plugins/ directory. After removing these everything worked as intended.