Edit: this has ceased to be relavant.

One of the things missing from 64bit computing at this moment is the Adobe Flash player. This severely limits your ability to spend countless hours on Youtube and/or most of the embedded video sites. Turns out Adobe has been especially slow releasing a 64bit solution, so we'll have to make do with a trick. AFAIK the 32bit flash player is 'wrapped' in ndiswrapper and then installed into your 63 bit Firefox.

You can follow these instructions to install the 32bit Firefox (thus skirting around the problem), or you can use this script to install and config the ndiswrapper work-around for your 64bit Firefox.

Tested and works here on Kubuntu Feisty 64bit.