While I am only running Fedora i386, I have not had any trouble whatsoever with Ubuntu 10.4 64 running Chromium as far as Flash is concerned. I used Ubuntu on my 64bit machine as Canonical does a pretty decent job in keeping things straight forward, without having to hunt around too much. At any rate, good luck!
[A bit off topic] do Amazon or MediaMonkey allow for music to be downloaded in FLAC format? I've been looking for a good music store that serves lossless music.
Laptop is a dual boot Mac/Windows 7 32 bit (tried VMWare but too laggy for graphics work), this is my main computer.
PC Desktop Windows 7 64 bit
Mac Desktop - Snow Leopard
Both desktops sit side by side.