A while ago, I wrote a short tutorial as to how to install the 32-bit Flash on a 64-bit Linux. Well, it's no longer needed, since a couple of days ago, Adobe finally released a 64-bit version of Flash 10 for Linux/Solaris. Available at:
http://labs.adobe.com/technologies/flashplayer10/ This is a prerelease version, so it's a bit slow, and has a bug I've seen with full screen refreshes, but it's much better then before. Yay Adobe.
A Windows version will probably appear sometime soon.