I have for some time had problems with flash videos in Firefox on my AMD64 Ubuntu machine. I normally use the computer for work so it has not really been that much of a problem. However, I hate not being able to use Ubuntu the way you would expect it to work … A Google search later, I found these simple instructions. Just follow the instructions and you will have flash videos working in no time. If you want to test your flash player on your AMD64 Ubuntu machine, you may check of EpicBattleAxe video above.
By the way, the new Ubuntu 9.10 looks and feels quite good 